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!