Preventing Deletions with triggers

I would like to have a trigger that fires whenever a delete is attempted.
The trigger should update the status field of the tupple (to remove the
tupple form the active set of tupples).

Here is what I got:

CREATE or replace FUNCTION person_fake_delete() RETURNS TRIGGER AS '
BEGIN
OLD.status := 1; -- This does the fake deletion
RETURN NULL; -- I thought this would prevent the delete from
actually happening.
END;
' LANGUAGE 'plpgsql';

create trigger person_fake_delete
before delete on person
for each row EXECUTE PROCEDURE
person_fake_delete();

This however does not work. the tupple is still deleted from the
table. Any Ideas?

Thanks,
Jeff Post