I think you have to make a distinction between banning or making a group illegal and finding different ways to curtail their public activities. As far as I know, there have been attempts to do that, as reported in today's newspapers. In Australia they're still debating criminalizing bikie gangs, as they call them, but they're having some constitutional issues. I believe it was tried in a couple of European countries without much success.
On October 22nd, 2009. See this statement in context.