Generally authorization for native mobile apps is enforced at the back-end API. After a user authenticates, the application will call a back-end API with the OAuth 2.0 access token. If the token has expired, is not valid or the authorizations provided in the access token are not sufficient for the request, then the API call will fail. The application should handle these failures gracefully.
The application itself may also enforce access control based on the attributes returned in the user profile. For example and enterprise application may only be available for user's in the finance department. If an enterprise user from marketing launches the mobile app, they may be denied access because of their user profile attributes.