diff --git a/google/cloud/servicemanagement_v1/services/service_manager/async_client.py b/google/cloud/servicemanagement_v1/services/service_manager/async_client.py
index c7e9e61..0095389 100644
--- a/google/cloud/servicemanagement_v1/services/service_manager/async_client.py
+++ b/google/cloud/servicemanagement_v1/services/service_manager/async_client.py
@@ -20,13 +20,15 @@
 import pkg_resources
 import warnings
 
-import google.api_core.client_options as ClientOptions  # type: ignore
+from google.api_core.client_options import ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.api import auth_pb2  # type: ignore
 from google.api import backend_pb2  # type: ignore
 from google.api import billing_pb2  # type: ignore
@@ -191,11 +193,11 @@ def __init__(
 
     async def list_services(
         self,
-        request: servicemanager.ListServicesRequest = None,
+        request: Union[servicemanager.ListServicesRequest, dict] = None,
         *,
         producer_project_id: str = None,
         consumer_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListServicesAsyncPager:
@@ -210,7 +212,7 @@ async def list_services(
         ``consumer_id`` must have the format of "project:{PROJECT-ID}".
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.ListServicesRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.ListServicesRequest, dict]):
                 The request object. Request message for `ListServices`
                 method.
             producer_project_id (:class:`str`):
@@ -286,10 +288,10 @@ async def list_services(
 
     async def get_service(
         self,
-        request: servicemanager.GetServiceRequest = None,
+        request: Union[servicemanager.GetServiceRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> resources.ManagedService:
@@ -297,7 +299,7 @@ async def get_service(
         unless the service is public.
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.GetServiceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.GetServiceRequest, dict]):
                 The request object. Request message for `GetService`
                 method.
             service_name (:class:`str`):
@@ -354,10 +356,10 @@ async def get_service(
 
     async def create_service(
         self,
-        request: servicemanager.CreateServiceRequest = None,
+        request: Union[servicemanager.CreateServiceRequest, dict] = None,
         *,
         service: resources.ManagedService = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -367,7 +369,7 @@ async def create_service(
         Operation<response: ManagedService>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.CreateServiceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.CreateServiceRequest, dict]):
                 The request object. Request message for CreateService
                 method.
             service (:class:`google.cloud.servicemanagement_v1.types.ManagedService`):
@@ -432,10 +434,10 @@ async def create_service(
 
     async def delete_service(
         self,
-        request: servicemanager.DeleteServiceRequest = None,
+        request: Union[servicemanager.DeleteServiceRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -449,7 +451,7 @@ async def delete_service(
         Operation<response: google.protobuf.Empty>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.DeleteServiceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.DeleteServiceRequest, dict]):
                 The request object. Request message for DeleteService
                 method.
             service_name (:class:`str`):
@@ -527,10 +529,10 @@ async def delete_service(
 
     async def undelete_service(
         self,
-        request: servicemanager.UndeleteServiceRequest = None,
+        request: Union[servicemanager.UndeleteServiceRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -543,7 +545,7 @@ async def undelete_service(
         Operation<response: UndeleteServiceResponse>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.UndeleteServiceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.UndeleteServiceRequest, dict]):
                 The request object. Request message for UndeleteService
                 method.
             service_name (:class:`str`):
@@ -611,10 +613,10 @@ async def undelete_service(
 
     async def list_service_configs(
         self,
-        request: servicemanager.ListServiceConfigsRequest = None,
+        request: Union[servicemanager.ListServiceConfigsRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListServiceConfigsAsyncPager:
@@ -622,7 +624,7 @@ async def list_service_configs(
         managed service, from the newest to the oldest.
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.ListServiceConfigsRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.ListServiceConfigsRequest, dict]):
                 The request object. Request message for
                 ListServiceConfigs method.
             service_name (:class:`str`):
@@ -688,12 +690,12 @@ async def list_service_configs(
 
     async def get_service_config(
         self,
-        request: servicemanager.GetServiceConfigRequest = None,
+        request: Union[servicemanager.GetServiceConfigRequest, dict] = None,
         *,
         service_name: str = None,
         config_id: str = None,
         view: servicemanager.GetServiceConfigRequest.ConfigView = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> service_pb2.Service:
@@ -701,7 +703,7 @@ async def get_service_config(
         service.
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.GetServiceConfigRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.GetServiceConfigRequest, dict]):
                 The request object. Request message for GetServiceConfig
                 method.
             service_name (:class:`str`):
@@ -796,11 +798,11 @@ async def get_service_config(
 
     async def create_service_config(
         self,
-        request: servicemanager.CreateServiceConfigRequest = None,
+        request: Union[servicemanager.CreateServiceConfigRequest, dict] = None,
         *,
         service_name: str = None,
         service_config: service_pb2.Service = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> service_pb2.Service:
@@ -815,7 +817,7 @@ async def create_service_config(
         rest will be deleted eventually.
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.CreateServiceConfigRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.CreateServiceConfigRequest, dict]):
                 The request object. Request message for
                 CreateServiceConfig method.
             service_name (:class:`str`):
@@ -898,12 +900,12 @@ async def create_service_config(
 
     async def submit_config_source(
         self,
-        request: servicemanager.SubmitConfigSourceRequest = None,
+        request: Union[servicemanager.SubmitConfigSourceRequest, dict] = None,
         *,
         service_name: str = None,
         config_source: resources.ConfigSource = None,
         validate_only: bool = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -922,7 +924,7 @@ async def submit_config_source(
         Operation<response: SubmitConfigSourceResponse>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.SubmitConfigSourceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.SubmitConfigSourceRequest, dict]):
                 The request object. Request message for
                 SubmitConfigSource method.
             service_name (:class:`str`):
@@ -1010,11 +1012,11 @@ async def submit_config_source(
 
     async def list_service_rollouts(
         self,
-        request: servicemanager.ListServiceRolloutsRequest = None,
+        request: Union[servicemanager.ListServiceRolloutsRequest, dict] = None,
         *,
         service_name: str = None,
         filter: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListServiceRolloutsAsyncPager:
@@ -1023,7 +1025,7 @@ async def list_service_rollouts(
         oldest.
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.ListServiceRolloutsRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.ListServiceRolloutsRequest, dict]):
                 The request object. Request message for
                 'ListServiceRollouts'
             service_name (:class:`str`):
@@ -1105,11 +1107,11 @@ async def list_service_rollouts(
 
     async def get_service_rollout(
         self,
-        request: servicemanager.GetServiceRolloutRequest = None,
+        request: Union[servicemanager.GetServiceRolloutRequest, dict] = None,
         *,
         service_name: str = None,
         rollout_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> resources.Rollout:
@@ -1117,7 +1119,7 @@ async def get_service_rollout(
         [rollout][google.api.servicemanagement.v1.Rollout].
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.GetServiceRolloutRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.GetServiceRolloutRequest, dict]):
                 The request object. Request message for
                 GetServiceRollout method.
             service_name (:class:`str`):
@@ -1187,11 +1189,11 @@ async def get_service_rollout(
 
     async def create_service_rollout(
         self,
-        request: servicemanager.CreateServiceRolloutRequest = None,
+        request: Union[servicemanager.CreateServiceRolloutRequest, dict] = None,
         *,
         service_name: str = None,
         rollout: resources.Rollout = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -1214,7 +1216,7 @@ async def create_service_rollout(
         Operation<response: Rollout>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.CreateServiceRolloutRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.CreateServiceRolloutRequest, dict]):
                 The request object. Request message for
                 'CreateServiceRollout'
             service_name (:class:`str`):
@@ -1292,11 +1294,11 @@ async def create_service_rollout(
 
     async def generate_config_report(
         self,
-        request: servicemanager.GenerateConfigReportRequest = None,
+        request: Union[servicemanager.GenerateConfigReportRequest, dict] = None,
         *,
         new_config: any_pb2.Any = None,
         old_config: any_pb2.Any = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> servicemanager.GenerateConfigReportResponse:
@@ -1314,7 +1316,7 @@ async def generate_config_report(
         the last pushed service configuration.
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.GenerateConfigReportRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.GenerateConfigReportRequest, dict]):
                 The request object. Request message for
                 GenerateConfigReport method.
             new_config (:class:`google.protobuf.any_pb2.Any`):
@@ -1386,11 +1388,11 @@ async def generate_config_report(
 
     async def enable_service(
         self,
-        request: servicemanager.EnableServiceRequest = None,
+        request: Union[servicemanager.EnableServiceRequest, dict] = None,
         *,
         service_name: str = None,
         consumer_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -1403,7 +1405,7 @@ async def enable_service(
         Operation<response: EnableServiceResponse>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.EnableServiceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.EnableServiceRequest, dict]):
                 The request object. Request message for EnableService
                 method.
             service_name (:class:`str`):
@@ -1491,11 +1493,11 @@ async def enable_service(
 
     async def disable_service(
         self,
-        request: servicemanager.DisableServiceRequest = None,
+        request: Union[servicemanager.DisableServiceRequest, dict] = None,
         *,
         service_name: str = None,
         consumer_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -1508,7 +1510,7 @@ async def disable_service(
         Operation<response: DisableServiceResponse>
 
         Args:
-            request (:class:`google.cloud.servicemanagement_v1.types.DisableServiceRequest`):
+            request (Union[google.cloud.servicemanagement_v1.types.DisableServiceRequest, dict]):
                 The request object. Request message for DisableService
                 method.
             service_name (:class:`str`):
diff --git a/google/cloud/servicemanagement_v1/services/service_manager/client.py b/google/cloud/servicemanagement_v1/services/service_manager/client.py
index 08b07b3..e43ca66 100644
--- a/google/cloud/servicemanagement_v1/services/service_manager/client.py
+++ b/google/cloud/servicemanagement_v1/services/service_manager/client.py
@@ -31,6 +31,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.api import auth_pb2  # type: ignore
 from google.api import backend_pb2  # type: ignore
 from google.api import billing_pb2  # type: ignore
@@ -367,7 +369,7 @@ def list_services(
         *,
         producer_project_id: str = None,
         consumer_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListServicesPager:
@@ -461,7 +463,7 @@ def get_service(
         request: Union[servicemanager.GetServiceRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> resources.ManagedService:
@@ -529,7 +531,7 @@ def create_service(
         request: Union[servicemanager.CreateServiceRequest, dict] = None,
         *,
         service: resources.ManagedService = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -607,7 +609,7 @@ def delete_service(
         request: Union[servicemanager.DeleteServiceRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -702,7 +704,7 @@ def undelete_service(
         request: Union[servicemanager.UndeleteServiceRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -786,7 +788,7 @@ def list_service_configs(
         request: Union[servicemanager.ListServiceConfigsRequest, dict] = None,
         *,
         service_name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListServiceConfigsPager:
@@ -865,7 +867,7 @@ def get_service_config(
         service_name: str = None,
         config_id: str = None,
         view: servicemanager.GetServiceConfigRequest.ConfigView = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> service_pb2.Service:
@@ -972,7 +974,7 @@ def create_service_config(
         *,
         service_name: str = None,
         service_config: service_pb2.Service = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> service_pb2.Service:
@@ -1075,7 +1077,7 @@ def submit_config_source(
         service_name: str = None,
         config_source: resources.ConfigSource = None,
         validate_only: bool = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -1186,7 +1188,7 @@ def list_service_rollouts(
         *,
         service_name: str = None,
         filter: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListServiceRolloutsPager:
@@ -1281,7 +1283,7 @@ def get_service_rollout(
         *,
         service_name: str = None,
         rollout_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> resources.Rollout:
@@ -1363,7 +1365,7 @@ def create_service_rollout(
         *,
         service_name: str = None,
         rollout: resources.Rollout = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -1468,7 +1470,7 @@ def generate_config_report(
         *,
         new_config: any_pb2.Any = None,
         old_config: any_pb2.Any = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> servicemanager.GenerateConfigReportResponse:
@@ -1562,7 +1564,7 @@ def enable_service(
         *,
         service_name: str = None,
         consumer_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -1667,7 +1669,7 @@ def disable_service(
         *,
         service_name: str = None,
         consumer_id: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
diff --git a/google/cloud/servicemanagement_v1/services/service_manager/transports/base.py b/google/cloud/servicemanagement_v1/services/service_manager/transports/base.py
index cd6d02b..46068a8 100644
--- a/google/cloud/servicemanagement_v1/services/service_manager/transports/base.py
+++ b/google/cloud/servicemanagement_v1/services/service_manager/transports/base.py
@@ -15,7 +15,6 @@
 #
 import abc
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Union
-import packaging.version
 import pkg_resources
 
 import google.auth  # type: ignore
@@ -41,15 +40,6 @@
 except pkg_resources.DistributionNotFound:
     DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo()
 
-try:
-    # google.auth.__version__ was added in 1.26.0
-    _GOOGLE_AUTH_VERSION = google.auth.__version__
-except AttributeError:
-    try:  # try pkg_resources if it is available
-        _GOOGLE_AUTH_VERSION = pkg_resources.get_distribution("google-auth").version
-    except pkg_resources.DistributionNotFound:  # pragma: NO COVER
-        _GOOGLE_AUTH_VERSION = None
-
 
 class ServiceManagerTransport(abc.ABC):
     """Abstract transport class for ServiceManager."""
@@ -104,7 +94,7 @@ def __init__(
             host += ":443"
         self._host = host
 
-        scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
+        scopes_kwargs = {"scopes": scopes, "default_scopes": self.AUTH_SCOPES}
 
         # Save the scopes.
         self._scopes = scopes
@@ -137,29 +127,6 @@ def __init__(
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): This method is in the base transport
-    # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-auth is increased.
-
-    # TODO: Remove this function once google-auth >= 1.25.0 is required
-    @classmethod
-    def _get_scopes_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Optional[Sequence[str]]]:
-        """Returns scopes kwargs to pass to google-auth methods depending on the google-auth version"""
-
-        scopes_kwargs = {}
-
-        if _GOOGLE_AUTH_VERSION and (
-            packaging.version.parse(_GOOGLE_AUTH_VERSION)
-            >= packaging.version.parse("1.25.0")
-        ):
-            scopes_kwargs = {"scopes": scopes, "default_scopes": cls.AUTH_SCOPES}
-        else:
-            scopes_kwargs = {"scopes": scopes or cls.AUTH_SCOPES}
-
-        return scopes_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
@@ -232,7 +199,7 @@ def close(self):
         raise NotImplementedError()
 
     @property
-    def operations_client(self) -> operations_v1.OperationsClient:
+    def operations_client(self):
         """Return the client designed to process long-running operations."""
         raise NotImplementedError()
 
diff --git a/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc.py b/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc.py
index 579aa1b..f764ac1 100644
--- a/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc.py
+++ b/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc.py
@@ -115,7 +115,7 @@ def __init__(
         self._grpc_channel = None
         self._ssl_channel_credentials = ssl_channel_credentials
         self._stubs: Dict[str, Callable] = {}
-        self._operations_client = None
+        self._operations_client: Optional[operations_v1.OperationsClient] = None
 
         if api_mtls_endpoint:
             warnings.warn("api_mtls_endpoint is deprecated", DeprecationWarning)
diff --git a/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc_asyncio.py b/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc_asyncio.py
index 451e2bd..cf85afb 100644
--- a/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc_asyncio.py
+++ b/google/cloud/servicemanagement_v1/services/service_manager/transports/grpc_asyncio.py
@@ -21,7 +21,6 @@
 from google.api_core import operations_v1  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
-import packaging.version
 
 import grpc  # type: ignore
 from grpc.experimental import aio  # type: ignore
@@ -162,7 +161,7 @@ def __init__(
         self._grpc_channel = None
         self._ssl_channel_credentials = ssl_channel_credentials
         self._stubs: Dict[str, Callable] = {}
-        self._operations_client = None
+        self._operations_client: Optional[operations_v1.OperationsAsyncClient] = None
 
         if api_mtls_endpoint:
             warnings.warn("api_mtls_endpoint is deprecated", DeprecationWarning)
diff --git a/google/cloud/servicemanagement_v1/types/resources.py b/google/cloud/servicemanagement_v1/types/resources.py
index 7e0cee2..3a273db 100644
--- a/google/cloud/servicemanagement_v1/types/resources.py
+++ b/google/cloud/servicemanagement_v1/types/resources.py
@@ -209,6 +209,13 @@ class Rollout(proto.Message):
     create a new version of the service config, and then create a
     Rollout to push the service config.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         rollout_id (str):
             Optional. Unique identifier of this Rollout. Must be no
@@ -233,9 +240,11 @@ class Rollout(proto.Message):
         traffic_percent_strategy (google.cloud.servicemanagement_v1.types.Rollout.TrafficPercentStrategy):
             Google Service Control selects service
             configurations based on traffic percentage.
+            This field is a member of `oneof`_ ``strategy``.
         delete_service_strategy (google.cloud.servicemanagement_v1.types.Rollout.DeleteServiceStrategy):
             The strategy associated with a rollout to delete a
             ``ManagedService``. Readonly.
+            This field is a member of `oneof`_ ``strategy``.
         service_name (str):
             The name of the service associated with this
             Rollout.
diff --git a/setup.py b/setup.py
index 0d2d38d..5581efd 100644
--- a/setup.py
+++ b/setup.py
@@ -28,10 +28,9 @@
     # NOTE: Maintainers, please do not require google-api-core>=2.x.x
     # Until this issue is closed
     # https://github.com/googleapis/google-cloud-python/issues/10566
-    "google-api-core[grpc] >= 1.26.0, <3.0.0dev",
+    "google-api-core[grpc] >= 1.28.0, <3.0.0dev",
     "libcst >= 0.2.5",
     "proto-plus >= 1.15.0",
-    "packaging >= 14.3",
 ]
 
 package_root = os.path.abspath(os.path.dirname(__file__))
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index ce8cfca..21fe240 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -19,8 +19,6 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-google-api-core==1.26.0
+google-api-core==1.28.0
 libcst==0.2.5
 proto-plus==1.15.0
-packaging==14.3
-google-auth==1.24.0  # TODO: remove when google-auth>=1.25.0 si transitively required through google-api-core
diff --git a/tests/unit/gapic/servicemanagement_v1/test_service_manager.py b/tests/unit/gapic/servicemanagement_v1/test_service_manager.py
index 50f2bdc..f860d96 100644
--- a/tests/unit/gapic/servicemanagement_v1/test_service_manager.py
+++ b/tests/unit/gapic/servicemanagement_v1/test_service_manager.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -63,9 +62,6 @@
 )
 from google.cloud.servicemanagement_v1.services.service_manager import pagers
 from google.cloud.servicemanagement_v1.services.service_manager import transports
-from google.cloud.servicemanagement_v1.services.service_manager.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.servicemanagement_v1.types import resources
 from google.cloud.servicemanagement_v1.types import servicemanager
 from google.longrunning import operations_pb2
@@ -80,20 +76,6 @@
 import google.auth
 
 
-# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
-# through google-api-core:
-# - Delete the auth "less than" test cases
-# - Delete these pytest markers (Make the "greater than or equal to" tests the default).
-requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth < 1.25.0",
-)
-requires_google_auth_gte_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) < packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth >= 1.25.0",
-)
-
-
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
 
@@ -250,7 +232,7 @@ def test_service_manager_client_client_options(
     options = client_options.ClientOptions(api_endpoint="squid.clam.whelk")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -267,7 +249,7 @@ def test_service_manager_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "never"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -284,7 +266,7 @@ def test_service_manager_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "always"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -313,7 +295,7 @@ def test_service_manager_client_client_options(
     options = client_options.ClientOptions(quota_project_id="octopus")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -372,7 +354,7 @@ def test_service_manager_client_mtls_env_auto(
         )
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class(client_options=options)
+            client = client_class(transport=transport_name, client_options=options)
 
             if use_client_cert_env == "false":
                 expected_client_cert_source = None
@@ -414,7 +396,7 @@ def test_service_manager_client_mtls_env_auto(
                         expected_client_cert_source = client_cert_source_callback
 
                     patched.return_value = None
-                    client = client_class()
+                    client = client_class(transport=transport_name)
                     patched.assert_called_once_with(
                         credentials=None,
                         credentials_file=None,
@@ -436,7 +418,7 @@ def test_service_manager_client_mtls_env_auto(
                 return_value=False,
             ):
                 patched.return_value = None
-                client = client_class()
+                client = client_class(transport=transport_name)
                 patched.assert_called_once_with(
                     credentials=None,
                     credentials_file=None,
@@ -467,7 +449,7 @@ def test_service_manager_client_client_options_scopes(
     options = client_options.ClientOptions(scopes=["1", "2"],)
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -498,7 +480,7 @@ def test_service_manager_client_client_options_credentials_file(
     options = client_options.ClientOptions(credentials_file="credentials.json")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file="credentials.json",
@@ -3609,7 +3591,6 @@ def test_service_manager_base_transport():
         transport.operations_client
 
 
-@requires_google_auth_gte_1_25_0
 def test_service_manager_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -3635,31 +3616,6 @@ def test_service_manager_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_service_manager_base_transport_with_credentials_file_old_google_auth():
-    # Instantiate the base transport with a credentials file
-    with mock.patch.object(
-        google.auth, "load_credentials_from_file", autospec=True
-    ) as load_creds, mock.patch(
-        "google.cloud.servicemanagement_v1.services.service_manager.transports.ServiceManagerTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.ServiceManagerTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=(
-                "https://www.googleapis.com/auth/cloud-platform",
-                "https://www.googleapis.com/auth/cloud-platform.read-only",
-                "https://www.googleapis.com/auth/service.management",
-                "https://www.googleapis.com/auth/service.management.readonly",
-            ),
-            quota_project_id="octopus",
-        )
-
-
 def test_service_manager_base_transport_with_adc():
     # Test the default credentials are used if credentials and credentials_file are None.
     with mock.patch.object(google.auth, "default", autospec=True) as adc, mock.patch(
@@ -3671,7 +3627,6 @@ def test_service_manager_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_service_manager_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -3689,23 +3644,6 @@ def test_service_manager_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_service_manager_auth_adc_old_google_auth():
-    # If no credentials are provided, we should use ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        ServiceManagerClient()
-        adc.assert_called_once_with(
-            scopes=(
-                "https://www.googleapis.com/auth/cloud-platform",
-                "https://www.googleapis.com/auth/cloud-platform.read-only",
-                "https://www.googleapis.com/auth/service.management",
-                "https://www.googleapis.com/auth/service.management.readonly",
-            ),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -3713,7 +3651,6 @@ def test_service_manager_auth_adc_old_google_auth():
         transports.ServiceManagerGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_service_manager_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -3732,31 +3669,6 @@ def test_service_manager_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.ServiceManagerGrpcTransport,
-        transports.ServiceManagerGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_service_manager_transport_auth_adc_old_google_auth(transport_class):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport_class(quota_project_id="octopus")
-        adc.assert_called_once_with(
-            scopes=(
-                "https://www.googleapis.com/auth/cloud-platform",
-                "https://www.googleapis.com/auth/cloud-platform.read-only",
-                "https://www.googleapis.com/auth/service.management",
-                "https://www.googleapis.com/auth/service.management.readonly",
-            ),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [