I would say "vigilante" defines it best.
your not quite law enforcement, as you help yourself to cargo and deal with black markets.
not quite a pirate, because you only persecute known criminals, and not your fellow citizenry
not quite a mercenary because no one pays you for this duty
and "traffic monitor/trash collector" isn't glamorous enough
and "because i'm BATMAN!!" is a bit over the top
so, vigilante.

you won't officially be a Lone Wolf Bounty Hunter Fett, until a legal Salvage License sort of thing exists.