For an injuction like that(I believe that's what you're referring to, SB, unless I'm mistaken) there has to be a certain area, groups and matching identifying appearance of some sorts for it to work.

For instance, as it works on gangs: Gang apparel, each gang has a different team they use to identify themselves, colors, tattoos and of course, a certain turf. You can't do that to mafia.

As far as MCs go, they're mainly started as a movement or simply a club. Hells Angels are a corporation(if I'm not mistaken) who have legal representatives and codemarked their logo. I know that when I played GTA SA:MP, Hells Angels lawyer would sign up to certain forums and threaten to sue people who made mods for the game based on Hells Angels(used the logo and whatnot). MCs aren't strictly criminal empires.