Should the session check a negative authorisation?

[Richard Hughes]

In https://bugzilla.redhat.com/show_bug.cgi?id=515769 a user has set
the PolicyKit action for shutting down the system policy as "no". This
means that any request to shutdown the computer will be denied.
Logically, I shouldn't even offer the shutdown button for
gnome-packagekit in ths case, and just add a note to the user.

So, should I do:

polkit_authority_check_authorization
polkit_authorization_result_get_is_authorized

to get the negative authorisation? Or is there an easier way?

Help welcome. Thanks,

Richard.