If you've fed him, you own him...
or, as others have pointed out, he owns you.

A neighbor's cat keeps hanging around our place
acting like he lives here rather than there. Our hard
and fast rules - he doesn't get fed here and he doesn't
come inside. For one thing, one of our resident cats
won't tolerate being near him. Good thing for us, we
know where he's *supposed* to be.
If only we could convince *him* of that.
(Actually, he's very sweet and friendly to us)