I have a catalog ( in unity catalog) containing multiple schemas.  I need an AD group to have select permission on all the schemas so at catalog level I granted Select to AD grp.  Then, I need to revoke permission on one particular schema in this catalog from the AD group ( actually a user in the AD grp).   I tried revoking schema-level access from the AD group and also from the user, but the group & user are still able to access.  Is there an issue?