Trigger with superuser privileges

Anobody could tell-me how can I make a Trigger thats execute some things
whith "postgres" superuser privileges (like INSERT INTO a table that the
user logged in don't have access)

I think triggers should run with table-owner user permissions. That way you
could have a table owned by superuser, who then grants insert/update/delete
privileges to regular users.

But I'm not sure that's how things are done now. Anyone?