DRYing up between Helper and Controller

I have a few small methods as part of my authorisation scheme, These
mostly get used by controllers, but sometimes I want a template to
call them too.

For example, there are methods called is_editor?, is_author? and
is_publisher? currently in application.rb.

I am including/excluding elements for navigation in the user interface
based upon these roles. Therefore I want one definition of these
methods that "everyone" can use.

Whats the right rails way to achieve this?

Cheers, --Kip