The Dom Post has a better proposal for dealing with gangs than banning patches and tatoos:
Gangs are an evil, contributing nothing useful to society. But the way to deal with them is not to stop them identifying themselves – something that in practice will prove impossible – but for the police to use the extensive means at their disposal to harass them out of existence. They should tear down their fortified pa(d)s, cripple their drug businesses and prevent them gathering together in public places to intimidate and jeer at their fellow citizens, something that is already prohibited in law.
Police will know they’ve got the balance right when gang members decide of their own volition that wearing patches is not worth the trouble it invites.
I think banning gang patches is the wrong answer to the right problem.