Limiting User access

Assuming I have the user id in a controller, is there some sort of procedure to prevent a user from accessing specific pages and redirecting them to an appropriate spot?

For instance a user is not an admin but is trying to access an admin page - is there a built in function that would allow a redirect? I know I can do it on a function by function basis in each controller but was looking for a before_XXXX type of event.

Thanks!