diff --git a/google/cloud/accessapproval_v1/services/access_approval/async_client.py b/google/cloud/accessapproval_v1/services/access_approval/async_client.py
index 00db042..5c92c8f 100644
--- a/google/cloud/accessapproval_v1/services/access_approval/async_client.py
+++ b/google/cloud/accessapproval_v1/services/access_approval/async_client.py
@@ -19,13 +19,15 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-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.cloud.accessapproval_v1.services.access_approval import pagers
 from google.cloud.accessapproval_v1.types import accessapproval
 from google.protobuf import field_mask_pb2  # type: ignore
@@ -198,10 +200,10 @@ def __init__(
 
     async def list_approval_requests(
         self,
-        request: accessapproval.ListApprovalRequestsMessage = None,
+        request: Union[accessapproval.ListApprovalRequestsMessage, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListApprovalRequestsAsyncPager:
@@ -211,7 +213,7 @@ async def list_approval_requests(
         order is reverse chronological.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.ListApprovalRequestsMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.ListApprovalRequestsMessage, dict]):
                 The request object. Request to list approval requests.
             parent (:class:`str`):
                 The parent resource. This may be
@@ -290,10 +292,10 @@ async def list_approval_requests(
 
     async def get_approval_request(
         self,
-        request: accessapproval.GetApprovalRequestMessage = None,
+        request: Union[accessapproval.GetApprovalRequestMessage, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.ApprovalRequest:
@@ -301,7 +303,7 @@ async def get_approval_request(
         not exist.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.GetApprovalRequestMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.GetApprovalRequestMessage, dict]):
                 The request object. Request to get an approval request.
             name (:class:`str`):
                 Name of the approval request to
@@ -370,9 +372,9 @@ async def get_approval_request(
 
     async def approve_approval_request(
         self,
-        request: accessapproval.ApproveApprovalRequestMessage = None,
+        request: Union[accessapproval.ApproveApprovalRequestMessage, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.ApprovalRequest:
@@ -383,7 +385,7 @@ async def approve_approval_request(
         pending state.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.ApproveApprovalRequestMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.ApproveApprovalRequestMessage, dict]):
                 The request object. Request to approve an
                 ApprovalRequest.
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
@@ -423,9 +425,9 @@ async def approve_approval_request(
 
     async def dismiss_approval_request(
         self,
-        request: accessapproval.DismissApprovalRequestMessage = None,
+        request: Union[accessapproval.DismissApprovalRequestMessage, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.ApprovalRequest:
@@ -441,7 +443,7 @@ async def dismiss_approval_request(
         a pending state.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.DismissApprovalRequestMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.DismissApprovalRequestMessage, dict]):
                 The request object. Request to dismiss an approval
                 request.
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
@@ -481,10 +483,10 @@ async def dismiss_approval_request(
 
     async def get_access_approval_settings(
         self,
-        request: accessapproval.GetAccessApprovalSettingsMessage = None,
+        request: Union[accessapproval.GetAccessApprovalSettingsMessage, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.AccessApprovalSettings:
@@ -492,7 +494,7 @@ async def get_access_approval_settings(
         or organization.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.GetAccessApprovalSettingsMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.GetAccessApprovalSettingsMessage, dict]):
                 The request object. Request to get access approval
                 settings.
             name (:class:`str`):
@@ -563,11 +565,11 @@ async def get_access_approval_settings(
 
     async def update_access_approval_settings(
         self,
-        request: accessapproval.UpdateAccessApprovalSettingsMessage = None,
+        request: Union[accessapproval.UpdateAccessApprovalSettingsMessage, dict] = None,
         *,
         settings: accessapproval.AccessApprovalSettings = None,
         update_mask: field_mask_pb2.FieldMask = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.AccessApprovalSettings:
@@ -576,7 +578,7 @@ async def update_access_approval_settings(
         field_mask.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.UpdateAccessApprovalSettingsMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.UpdateAccessApprovalSettingsMessage, dict]):
                 The request object. Request to update access approval
                 settings.
             settings (:class:`google.cloud.accessapproval_v1.types.AccessApprovalSettings`):
@@ -656,10 +658,10 @@ async def update_access_approval_settings(
 
     async def delete_access_approval_settings(
         self,
-        request: accessapproval.DeleteAccessApprovalSettingsMessage = None,
+        request: Union[accessapproval.DeleteAccessApprovalSettingsMessage, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> None:
@@ -673,7 +675,7 @@ async def delete_access_approval_settings(
         inherited.
 
         Args:
-            request (:class:`google.cloud.accessapproval_v1.types.DeleteAccessApprovalSettingsMessage`):
+            request (Union[google.cloud.accessapproval_v1.types.DeleteAccessApprovalSettingsMessage, dict]):
                 The request object. Request to delete access approval
                 settings.
             name (:class:`str`):
diff --git a/google/cloud/accessapproval_v1/services/access_approval/client.py b/google/cloud/accessapproval_v1/services/access_approval/client.py
index c2286d0..9af27f0 100644
--- a/google/cloud/accessapproval_v1/services/access_approval/client.py
+++ b/google/cloud/accessapproval_v1/services/access_approval/client.py
@@ -30,6 +30,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.accessapproval_v1.services.access_approval import pagers
 from google.cloud.accessapproval_v1.types import accessapproval
 from google.protobuf import field_mask_pb2  # type: ignore
@@ -373,7 +375,7 @@ def list_approval_requests(
         request: Union[accessapproval.ListApprovalRequestsMessage, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListApprovalRequestsPager:
@@ -456,7 +458,7 @@ def get_approval_request(
         request: Union[accessapproval.GetApprovalRequestMessage, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.ApprovalRequest:
@@ -526,7 +528,7 @@ def approve_approval_request(
         self,
         request: Union[accessapproval.ApproveApprovalRequestMessage, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.ApprovalRequest:
@@ -580,7 +582,7 @@ def dismiss_approval_request(
         self,
         request: Union[accessapproval.DismissApprovalRequestMessage, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.ApprovalRequest:
@@ -640,7 +642,7 @@ def get_access_approval_settings(
         request: Union[accessapproval.GetAccessApprovalSettingsMessage, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.AccessApprovalSettings:
@@ -716,7 +718,7 @@ def update_access_approval_settings(
         *,
         settings: accessapproval.AccessApprovalSettings = None,
         update_mask: field_mask_pb2.FieldMask = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> accessapproval.AccessApprovalSettings:
@@ -810,7 +812,7 @@ def delete_access_approval_settings(
         request: Union[accessapproval.DeleteAccessApprovalSettingsMessage, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> None:
diff --git a/google/cloud/accessapproval_v1/services/access_approval/transports/base.py b/google/cloud/accessapproval_v1/services/access_approval/transports/base.py
index 5a2f264..9175da9 100644
--- a/google/cloud/accessapproval_v1/services/access_approval/transports/base.py
+++ b/google/cloud/accessapproval_v1/services/access_approval/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
@@ -38,15 +37,6 @@
 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 AccessApprovalTransport(abc.ABC):
     """Abstract transport class for AccessApproval."""
@@ -96,7 +86,7 @@ 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
@@ -129,29 +119,6 @@ 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 = {
diff --git a/google/cloud/accessapproval_v1/services/access_approval/transports/grpc_asyncio.py b/google/cloud/accessapproval_v1/services/access_approval/transports/grpc_asyncio.py
index ad2188e..e1407bb 100644
--- a/google/cloud/accessapproval_v1/services/access_approval/transports/grpc_asyncio.py
+++ b/google/cloud/accessapproval_v1/services/access_approval/transports/grpc_asyncio.py
@@ -20,7 +20,6 @@
 from google.api_core import grpc_helpers_async  # 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
diff --git a/google/cloud/accessapproval_v1/types/accessapproval.py b/google/cloud/accessapproval_v1/types/accessapproval.py
index 6ef35da..6d78f27 100644
--- a/google/cloud/accessapproval_v1/types/accessapproval.py
+++ b/google/cloud/accessapproval_v1/types/accessapproval.py
@@ -163,6 +163,13 @@ class ResourceProperties(proto.Message):
 class ApprovalRequest(proto.Message):
     r"""A request for the customer to approve access to a resource.
 
+    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:
         name (str):
             The resource name of the request. Format is
@@ -194,8 +201,10 @@ class ApprovalRequest(proto.Message):
             time.
         approve (google.cloud.accessapproval_v1.types.ApproveDecision):
             Access was approved.
+            This field is a member of `oneof`_ ``decision``.
         dismiss (google.cloud.accessapproval_v1.types.DismissDecision):
             The request was dismissed.
+            This field is a member of `oneof`_ ``decision``.
     """
 
     name = proto.Field(proto.STRING, number=1,)
diff --git a/setup.py b/setup.py
index ff144b6..470e5f5 100644
--- a/setup.py
+++ b/setup.py
@@ -28,9 +28,8 @@
     # 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",
     "proto-plus >= 1.4.0",
-    "packaging >= 14.3",
 ]
 
 extras = {"libcst": "libcst >= 0.2.5"}
@@ -81,7 +80,7 @@
     scripts=["scripts/fixup_accessapproval_v1_keywords.py"],
     namespace_packages=namespaces,
     install_requires=dependencies,
-    extras_requires=extras,
+    extras_require=extras,
     include_package_data=True,
     zip_safe=False,
 )
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index 90b6c31..9e0fb5a 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -4,8 +4,6 @@
 # Pin the version to the lower bound.
 # e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have google-cloud-foo==1.14.0
-google-api-core==1.26.0
+google-api-core==1.28.0
 proto-plus==1.10.0
 libcst==0.2.5
-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/accessapproval_v1/test_access_approval.py b/tests/unit/gapic/accessapproval_v1/test_access_approval.py
index c2b26b4..f633082 100644
--- a/tests/unit/gapic/accessapproval_v1/test_access_approval.py
+++ b/tests/unit/gapic/accessapproval_v1/test_access_approval.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -38,9 +37,6 @@
 from google.cloud.accessapproval_v1.services.access_approval import AccessApprovalClient
 from google.cloud.accessapproval_v1.services.access_approval import pagers
 from google.cloud.accessapproval_v1.services.access_approval import transports
-from google.cloud.accessapproval_v1.services.access_approval.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.accessapproval_v1.types import accessapproval
 from google.oauth2 import service_account
 from google.protobuf import field_mask_pb2  # type: ignore
@@ -48,20 +44,6 @@
 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"
 
@@ -218,7 +200,7 @@ def test_access_approval_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,
@@ -235,7 +217,7 @@ def test_access_approval_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,
@@ -252,7 +234,7 @@ def test_access_approval_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,
@@ -281,7 +263,7 @@ def test_access_approval_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,
@@ -340,7 +322,7 @@ def test_access_approval_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
@@ -382,7 +364,7 @@ def test_access_approval_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,
@@ -404,7 +386,7 @@ def test_access_approval_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,
@@ -435,7 +417,7 @@ def test_access_approval_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,
@@ -466,7 +448,7 @@ def test_access_approval_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",
@@ -2233,7 +2215,6 @@ def test_access_approval_base_transport():
         transport.close()
 
 
-@requires_google_auth_gte_1_25_0
 def test_access_approval_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -2254,26 +2235,6 @@ def test_access_approval_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_access_approval_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.accessapproval_v1.services.access_approval.transports.AccessApprovalTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.AccessApprovalTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 def test_access_approval_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(
@@ -2285,7 +2246,6 @@ def test_access_approval_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_access_approval_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -2298,18 +2258,6 @@ def test_access_approval_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_access_approval_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)
-        AccessApprovalClient()
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -2317,7 +2265,6 @@ def test_access_approval_auth_adc_old_google_auth():
         transports.AccessApprovalGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_access_approval_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -2331,26 +2278,6 @@ def test_access_approval_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.AccessApprovalGrpcTransport,
-        transports.AccessApprovalGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_access_approval_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",),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [