diff --git a/.coveragerc b/.coveragerc
index 10654a7..463df93 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -2,7 +2,6 @@
 branch = True
 
 [report]
-fail_under = 100
 show_missing = True
 omit =
     google/cloud/networkconnectivity/__init__.py
diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index da616c9..e2b39f9 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-python:latest
-  digest: sha256:c66ba3c8d7bc8566f47df841f98cd0097b28fff0b1864c86f5817f4c8c3e8600
+  digest: sha256:99d90d097e4a4710cc8658ee0b5b963f4426d0e424819787c3ac1405c9a26719
diff --git a/.kokoro/samples/python3.9/common.cfg b/.kokoro/samples/python3.9/common.cfg
new file mode 100644
index 0000000..4a143a1
--- /dev/null
+++ b/.kokoro/samples/python3.9/common.cfg
@@ -0,0 +1,40 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Build logs will be here
+action {
+  define_artifacts {
+    regex: "**/*sponge_log.xml"
+  }
+}
+
+# Specify which tests to run
+env_vars: {
+    key: "RUN_TESTS_SESSION"
+    value: "py-3.9"
+}
+
+# Declare build specific Cloud project.
+env_vars: {
+    key: "BUILD_SPECIFIC_GCLOUD_PROJECT"
+    value: "python-docs-samples-tests-py39"
+}
+
+env_vars: {
+    key: "TRAMPOLINE_BUILD_FILE"
+    value: "github/python-network-connectivity/.kokoro/test-samples.sh"
+}
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+    key: "TRAMPOLINE_IMAGE"
+    value: "gcr.io/cloud-devrel-kokoro-resources/python-samples-testing-docker"
+}
+
+# Download secrets for samples
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
+
+# Download trampoline resources.
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
+
+# Use the trampoline script to run in docker.
+build_file: "python-network-connectivity/.kokoro/trampoline.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.9/continuous.cfg b/.kokoro/samples/python3.9/continuous.cfg
new file mode 100644
index 0000000..a1c8d97
--- /dev/null
+++ b/.kokoro/samples/python3.9/continuous.cfg
@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
\ No newline at end of file
diff --git a/.kokoro/samples/python3.9/periodic-head.cfg b/.kokoro/samples/python3.9/periodic-head.cfg
new file mode 100644
index 0000000..f9cfcd3
--- /dev/null
+++ b/.kokoro/samples/python3.9/periodic-head.cfg
@@ -0,0 +1,11 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
+
+env_vars: {
+    key: "TRAMPOLINE_BUILD_FILE"
+    value: "github/python-pubsub/.kokoro/test-samples-against-head.sh"
+}
diff --git a/.kokoro/samples/python3.9/periodic.cfg b/.kokoro/samples/python3.9/periodic.cfg
new file mode 100644
index 0000000..50fec96
--- /dev/null
+++ b/.kokoro/samples/python3.9/periodic.cfg
@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "False"
+}
\ No newline at end of file
diff --git a/.kokoro/samples/python3.9/presubmit.cfg b/.kokoro/samples/python3.9/presubmit.cfg
new file mode 100644
index 0000000..a1c8d97
--- /dev/null
+++ b/.kokoro/samples/python3.9/presubmit.cfg
@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
\ No newline at end of file
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4f00c7c..62eb5a7 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -16,7 +16,7 @@
 # See https://pre-commit.com/hooks.html for more hooks
 repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v3.4.0
+    rev: v4.0.1
     hooks:
     -   id: trailing-whitespace
     -   id: end-of-file-fixer
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 83ce002..642556d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,22 @@
 # Changelog
 
+## [0.4.0](https://www.github.com/googleapis/python-network-connectivity/compare/v0.3.0...v0.4.0) (2021-07-01)
+
+
+### Features
+
+* add always_use_jwt_access ([#48](https://www.github.com/googleapis/python-network-connectivity/issues/48)) ([dec3204](https://www.github.com/googleapis/python-network-connectivity/commit/dec3204223da36ff8c01ea2266c086ff459bce4d))
+
+
+### Bug Fixes
+
+* disable always_use_jwt_access ([#52](https://www.github.com/googleapis/python-network-connectivity/issues/52)) ([9c1ad1a](https://www.github.com/googleapis/python-network-connectivity/commit/9c1ad1aff188e97d4fdeaee812b670ba2f34df65))
+
+
+### Documentation
+
+* omit mention of Python 2.7 in 'CONTRIBUTING.rst' ([#1127](https://www.github.com/googleapis/python-network-connectivity/issues/1127)) ([#44](https://www.github.com/googleapis/python-network-connectivity/issues/44)) ([39475e1](https://www.github.com/googleapis/python-network-connectivity/commit/39475e101d8baaa235f20d7a52efc176f5e7de9e)), closes [#1126](https://www.github.com/googleapis/python-network-connectivity/issues/1126)
+
 ## [0.3.0](https://www.github.com/googleapis/python-network-connectivity/compare/v0.2.0...v0.3.0) (2021-06-16)
 
 
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index c592898..6433f18 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -68,15 +68,12 @@ Using ``nox``
 We use `nox <https://nox.readthedocs.io/en/latest/>`__ to instrument our tests.
 
 - To test your changes, run unit tests with ``nox``::
+    $ nox -s unit
 
-    $ nox -s unit-2.7
-    $ nox -s unit-3.8
-    $ ...
+- To run a single unit test::
 
-- Args to pytest can be passed through the nox command separated by a `--`. For
-  example, to run a single test::
+    $ nox -s unit-3.9 -- -k <name of test>
 
-    $ nox -s unit-3.8 -- -k <name of test>
 
   .. note::
 
@@ -143,8 +140,7 @@ Running System Tests
 - To run system tests, you can execute::
 
    # Run all system tests
-   $ nox -s system-3.8
-   $ nox -s system-2.7
+   $ nox -s system
 
    # Run a single system test
    $ nox -s system-3.8 -- -k <name of test>
@@ -152,9 +148,8 @@ Running System Tests
 
   .. note::
 
-      System tests are only configured to run under Python 2.7 and
-      Python 3.8. For expediency, we do not run them in older versions
-      of Python 3.
+      System tests are only configured to run under Python 3.8.
+      For expediency, we do not run them in older versions of Python 3.
 
   This alone will not run the tests. You'll need to change some local
   auth settings and change some configuration in your project to
@@ -218,8 +213,8 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 .. _config: https://github.com/googleapis/python-network-connectivity/blob/master/noxfile.py
 
 
-We also explicitly decided to support Python 3 beginning with version
-3.6. Reasons for this include:
+We also explicitly decided to support Python 3 beginning with version 3.6.
+Reasons for this include:
 
 -  Encouraging use of newest versions of Python 3
 -  Taking the lead of `prominent`_ open-source `projects`_
diff --git a/docs/conf.py b/docs/conf.py
index d1cb26e..aaa9165 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -80,9 +80,9 @@
 master_doc = "index"
 
 # General information about the project.
-project = u"google-cloud-network-connectivity"
-copyright = u"2019, Google"
-author = u"Google APIs"
+project = "google-cloud-network-connectivity"
+copyright = "2019, Google"
+author = "Google APIs"
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
@@ -281,7 +281,7 @@
     (
         master_doc,
         "google-cloud-network-connectivity.tex",
-        u"google-cloud-network-connectivity Documentation",
+        "google-cloud-network-connectivity Documentation",
         author,
         "manual",
     )
@@ -316,7 +316,7 @@
     (
         master_doc,
         "google-cloud-network-connectivity",
-        u"google-cloud-network-connectivity Documentation",
+        "google-cloud-network-connectivity Documentation",
         [author],
         1,
     )
@@ -335,7 +335,7 @@
     (
         master_doc,
         "google-cloud-network-connectivity",
-        u"google-cloud-network-connectivity Documentation",
+        "google-cloud-network-connectivity Documentation",
         author,
         "google-cloud-network-connectivity",
         "google-cloud-network-connectivity Library",
diff --git a/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/base.py b/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/base.py
index 3ccf6c6..8eb27eb 100644
--- a/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/base.py
+++ b/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/base.py
@@ -25,6 +25,7 @@
 from google.api_core import retry as retries  # type: ignore
 from google.api_core import operations_v1  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
+from google.oauth2 import service_account  # type: ignore
 
 from google.cloud.networkconnectivity_v1alpha1.types import hub
 from google.cloud.networkconnectivity_v1alpha1.types import hub as gcn_hub
@@ -48,8 +49,6 @@
     except pkg_resources.DistributionNotFound:  # pragma: NO COVER
         _GOOGLE_AUTH_VERSION = None
 
-_API_CORE_VERSION = google.api_core.__version__
-
 
 class HubServiceTransport(abc.ABC):
     """Abstract transport class for HubService."""
@@ -67,6 +66,7 @@ def __init__(
         scopes: Optional[Sequence[str]] = None,
         quota_project_id: Optional[str] = None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
         **kwargs,
     ) -> None:
         """Instantiate the transport.
@@ -90,6 +90,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
         """
         # Save the hostname. Default to port 443 (HTTPS) if none is specified.
         if ":" not in host:
@@ -99,7 +101,7 @@ def __init__(
         scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
 
         # Save the scopes.
-        self._scopes = scopes or self.AUTH_SCOPES
+        self._scopes = scopes
 
         # If no credentials are provided, then determine the appropriate
         # defaults.
@@ -118,13 +120,20 @@ def __init__(
                 **scopes_kwargs, quota_project_id=quota_project_id
             )
 
+        # If the credentials is service account credentials, then always try to use self signed JWT.
+        if (
+            always_use_jwt_access
+            and isinstance(credentials, service_account.Credentials)
+            and hasattr(service_account.Credentials, "with_always_use_jwt_access")
+        ):
+            credentials = credentials.with_always_use_jwt_access(True)
+
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): These two class methods are in the base transport
+    # 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-api-core
-    # and google-auth are increased.
+    # 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
@@ -145,27 +154,6 @@ def _get_scopes_kwargs(
 
         return scopes_kwargs
 
-    # TODO: Remove this function once google-api-core >= 1.26.0 is required
-    @classmethod
-    def _get_self_signed_jwt_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Union[Optional[Sequence[str]], str]]:
-        """Returns kwargs to pass to grpc_helpers.create_channel depending on the google-api-core version"""
-
-        self_signed_jwt_kwargs: Dict[str, Union[Optional[Sequence[str]], str]] = {}
-
-        if _API_CORE_VERSION and (
-            packaging.version.parse(_API_CORE_VERSION)
-            >= packaging.version.parse("1.26.0")
-        ):
-            self_signed_jwt_kwargs["default_scopes"] = cls.AUTH_SCOPES
-            self_signed_jwt_kwargs["scopes"] = scopes
-            self_signed_jwt_kwargs["default_host"] = cls.DEFAULT_HOST
-        else:
-            self_signed_jwt_kwargs["scopes"] = scopes or cls.AUTH_SCOPES
-
-        return self_signed_jwt_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
diff --git a/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc.py b/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc.py
index 4e763e1..a2472f3 100644
--- a/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc.py
+++ b/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc.py
@@ -63,6 +63,7 @@ def __init__(
         client_cert_source_for_mtls: Callable[[], Tuple[bytes, bytes]] = None,
         quota_project_id: Optional[str] = None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
     ) -> None:
         """Instantiate the transport.
 
@@ -103,6 +104,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
 
         Raises:
           google.auth.exceptions.MutualTLSChannelError: If mutual TLS transport
@@ -156,6 +159,7 @@ def __init__(
             scopes=scopes,
             quota_project_id=quota_project_id,
             client_info=client_info,
+            always_use_jwt_access=always_use_jwt_access,
         )
 
         if not self._grpc_channel:
@@ -211,14 +215,14 @@ def create_channel(
               and ``credentials_file`` are passed.
         """
 
-        self_signed_jwt_kwargs = cls._get_self_signed_jwt_kwargs(host, scopes)
-
         return grpc_helpers.create_channel(
             host,
             credentials=credentials,
             credentials_file=credentials_file,
             quota_project_id=quota_project_id,
-            **self_signed_jwt_kwargs,
+            default_scopes=cls.AUTH_SCOPES,
+            scopes=scopes,
+            default_host=cls.DEFAULT_HOST,
             **kwargs,
         )
 
diff --git a/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc_asyncio.py b/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc_asyncio.py
index 70865c7..6442757 100644
--- a/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc_asyncio.py
+++ b/google/cloud/networkconnectivity_v1alpha1/services/hub_service/transports/grpc_asyncio.py
@@ -84,14 +84,14 @@ def create_channel(
             aio.Channel: A gRPC AsyncIO channel object.
         """
 
-        self_signed_jwt_kwargs = cls._get_self_signed_jwt_kwargs(host, scopes)
-
         return grpc_helpers_async.create_channel(
             host,
             credentials=credentials,
             credentials_file=credentials_file,
             quota_project_id=quota_project_id,
-            **self_signed_jwt_kwargs,
+            default_scopes=cls.AUTH_SCOPES,
+            scopes=scopes,
+            default_host=cls.DEFAULT_HOST,
             **kwargs,
         )
 
@@ -109,6 +109,7 @@ def __init__(
         client_cert_source_for_mtls: Callable[[], Tuple[bytes, bytes]] = None,
         quota_project_id=None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
     ) -> None:
         """Instantiate the transport.
 
@@ -150,6 +151,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
 
         Raises:
             google.auth.exceptions.MutualTlsChannelError: If mutual TLS transport
@@ -202,6 +205,7 @@ def __init__(
             scopes=scopes,
             quota_project_id=quota_project_id,
             client_info=client_info,
+            always_use_jwt_access=always_use_jwt_access,
         )
 
         if not self._grpc_channel:
diff --git a/setup.py b/setup.py
index 44c7eea..4834dce 100644
--- a/setup.py
+++ b/setup.py
@@ -19,7 +19,7 @@
 import os
 import setuptools  # type: ignore
 
-version = "0.3.0"
+version = "0.4.0"
 
 package_root = os.path.abspath(os.path.dirname(__file__))
 
@@ -44,7 +44,7 @@
     platforms="Posix; MacOS X; Windows",
     include_package_data=True,
     install_requires=(
-        "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
+        "google-api-core[grpc] >= 1.26.0, <2.0.0dev",
         "proto-plus >= 1.4.0",
         "packaging >= 14.3",
     ),
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index a85c4a1..2955fcf 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -19,6 +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==1.22.2
+google-api-core==1.26.0
 proto-plus==1.4.0
 packaging==14.3
diff --git a/tests/unit/gapic/networkconnectivity_v1alpha1/test_hub_service.py b/tests/unit/gapic/networkconnectivity_v1alpha1/test_hub_service.py
index 907d23a..a43e09d 100644
--- a/tests/unit/gapic/networkconnectivity_v1alpha1/test_hub_service.py
+++ b/tests/unit/gapic/networkconnectivity_v1alpha1/test_hub_service.py
@@ -42,9 +42,6 @@
 )
 from google.cloud.networkconnectivity_v1alpha1.services.hub_service import pagers
 from google.cloud.networkconnectivity_v1alpha1.services.hub_service import transports
-from google.cloud.networkconnectivity_v1alpha1.services.hub_service.transports.base import (
-    _API_CORE_VERSION,
-)
 from google.cloud.networkconnectivity_v1alpha1.services.hub_service.transports.base import (
     _GOOGLE_AUTH_VERSION,
 )
@@ -58,8 +55,9 @@
 import google.auth
 
 
-# TODO(busunkim): Once google-api-core >= 1.26.0 is required:
-# - Delete all the api-core and auth "less than" test cases
+# 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"),
@@ -70,16 +68,6 @@
     reason="This test requires google-auth >= 1.25.0",
 )
 
-requires_api_core_lt_1_26_0 = pytest.mark.skipif(
-    packaging.version.parse(_API_CORE_VERSION) >= packaging.version.parse("1.26.0"),
-    reason="This test requires google-api-core < 1.26.0",
-)
-
-requires_api_core_gte_1_26_0 = pytest.mark.skipif(
-    packaging.version.parse(_API_CORE_VERSION) < packaging.version.parse("1.26.0"),
-    reason="This test requires google-api-core >= 1.26.0",
-)
-
 
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
@@ -137,6 +125,34 @@ def test_hub_service_client_from_service_account_info(client_class):
         assert client.transport._host == "networkconnectivity.googleapis.com:443"
 
 
+@pytest.mark.parametrize("client_class", [HubServiceClient, HubServiceAsyncClient,])
+def test_hub_service_client_service_account_always_use_jwt(client_class):
+    with mock.patch.object(
+        service_account.Credentials, "with_always_use_jwt_access", create=True
+    ) as use_jwt:
+        creds = service_account.Credentials(None, None, None)
+        client = client_class(credentials=creds)
+        use_jwt.assert_not_called()
+
+
+@pytest.mark.parametrize(
+    "transport_class,transport_name",
+    [
+        (transports.HubServiceGrpcTransport, "grpc"),
+        (transports.HubServiceGrpcAsyncIOTransport, "grpc_asyncio"),
+    ],
+)
+def test_hub_service_client_service_account_always_use_jwt_true(
+    transport_class, transport_name
+):
+    with mock.patch.object(
+        service_account.Credentials, "with_always_use_jwt_access", create=True
+    ) as use_jwt:
+        creds = service_account.Credentials(None, None, None)
+        transport = transport_class(credentials=creds, always_use_jwt_access=True)
+        use_jwt.assert_called_once_with(True)
+
+
 @pytest.mark.parametrize("client_class", [HubServiceClient, HubServiceAsyncClient,])
 def test_hub_service_client_from_service_account_file(client_class):
     creds = ga_credentials.AnonymousCredentials()
@@ -2956,7 +2972,6 @@ def test_hub_service_transport_auth_adc_old_google_auth(transport_class):
         (transports.HubServiceGrpcAsyncIOTransport, grpc_helpers_async),
     ],
 )
-@requires_api_core_gte_1_26_0
 def test_hub_service_transport_create_channel(transport_class, grpc_helpers):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -2985,79 +3000,6 @@ def test_hub_service_transport_create_channel(transport_class, grpc_helpers):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class,grpc_helpers",
-    [
-        (transports.HubServiceGrpcTransport, grpc_helpers),
-        (transports.HubServiceGrpcAsyncIOTransport, grpc_helpers_async),
-    ],
-)
-@requires_api_core_lt_1_26_0
-def test_hub_service_transport_create_channel_old_api_core(
-    transport_class, grpc_helpers
-):
-    # 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, mock.patch.object(
-        grpc_helpers, "create_channel", autospec=True
-    ) as create_channel:
-        creds = ga_credentials.AnonymousCredentials()
-        adc.return_value = (creds, None)
-        transport_class(quota_project_id="octopus")
-
-        create_channel.assert_called_with(
-            "networkconnectivity.googleapis.com:443",
-            credentials=creds,
-            credentials_file=None,
-            quota_project_id="octopus",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            ssl_credentials=None,
-            options=[
-                ("grpc.max_send_message_length", -1),
-                ("grpc.max_receive_message_length", -1),
-            ],
-        )
-
-
-@pytest.mark.parametrize(
-    "transport_class,grpc_helpers",
-    [
-        (transports.HubServiceGrpcTransport, grpc_helpers),
-        (transports.HubServiceGrpcAsyncIOTransport, grpc_helpers_async),
-    ],
-)
-@requires_api_core_lt_1_26_0
-def test_hub_service_transport_create_channel_user_scopes(
-    transport_class, grpc_helpers
-):
-    # 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, mock.patch.object(
-        grpc_helpers, "create_channel", autospec=True
-    ) as create_channel:
-        creds = ga_credentials.AnonymousCredentials()
-        adc.return_value = (creds, None)
-
-        transport_class(quota_project_id="octopus", scopes=["1", "2"])
-
-        create_channel.assert_called_with(
-            "networkconnectivity.googleapis.com:443",
-            credentials=creds,
-            credentials_file=None,
-            quota_project_id="octopus",
-            scopes=["1", "2"],
-            ssl_credentials=None,
-            options=[
-                ("grpc.max_send_message_length", -1),
-                ("grpc.max_receive_message_length", -1),
-            ],
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [transports.HubServiceGrpcTransport, transports.HubServiceGrpcAsyncIOTransport],
@@ -3077,7 +3019,7 @@ def test_hub_service_grpc_transport_client_cert_source_for_mtls(transport_class)
             "squid.clam.whelk:443",
             credentials=cred,
             credentials_file=None,
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
+            scopes=None,
             ssl_credentials=mock_ssl_channel_creds,
             quota_project_id=None,
             options=[
@@ -3181,7 +3123,7 @@ def test_hub_service_transport_channel_mtls_with_client_cert_source(transport_cl
                 "mtls.squid.clam.whelk:443",
                 credentials=cred,
                 credentials_file=None,
-                scopes=("https://www.googleapis.com/auth/cloud-platform",),
+                scopes=None,
                 ssl_credentials=mock_ssl_cred,
                 quota_project_id=None,
                 options=[
@@ -3225,7 +3167,7 @@ def test_hub_service_transport_channel_mtls_with_adc(transport_class):
                 "mtls.squid.clam.whelk:443",
                 credentials=mock_cred,
                 credentials_file=None,
-                scopes=("https://www.googleapis.com/auth/cloud-platform",),
+                scopes=None,
                 ssl_credentials=mock_ssl_cred,
                 quota_project_id=None,
                 options=[