diff --git a/google/oauth2/credentials.py b/google/oauth2/credentials.py
index 6a635dd..f1df887 100644
--- a/google/oauth2/credentials.py
+++ b/google/oauth2/credentials.py
@@ -36,7 +36,7 @@
 from google.oauth2 import _client
 
 
-class Credentials(credentials.Scoped, credentials.Credentials):
+class Credentials(credentials.ReadOnlyScoped, credentials.Credentials):
     """Credentials using OAuth 2.0 access and refresh tokens."""
 
     def __init__(self, token, refresh_token=None, id_token=None,
@@ -109,15 +109,6 @@
         the initial token is requested and can not be changed."""
         return False
 
-    def with_scopes(self, scopes):
-        """Unavailable, OAuth 2.0 credentials can not be re-scoped.
-
-        OAuth 2.0 credentials have their scopes set when the initial token is
-        requested and can not be changed.
-        """
-        raise NotImplementedError(
-            'OAuth 2.0 Credentials can not modify their scopes.')
-
     @_helpers.copy_docstring(credentials.Credentials)
     def refresh(self, request):
         access_token, refresh_token, expiry, grant_response = (