According to an article in the Reno Gazette Journal, police in Reno, Nevada are now treating "straight edge" as a gang following a number of attacks linked to the lifestyle. From the article:
You wouldn't expect a splinter faction of teens that rejects alcohol, tobacco, drugs or promiscuous sex to be an active criminal street gang, but in Washoe County that's exactly what's happening, authorities say.

In March - following a six-month investigation - Straight Edge was officially classified a gang by the Regional Gang Unit. Nearly every week, gang officers investigate Straight Edge crimes or harassment that doesn't seem to subside following arrests.

Authorities describe Straight Edge attacks as random, opportunistic, violent beatings that can be spurred by minor comments from nonmembers. Members - who sometimes use bats, shovels, knives, brass knuckles and Mace - don't engage in violence unless they can outnumber their targets, police said.
While police acknowledge that not every person claiming to adhere to the lifestyle engages in criminal activicity, Lt. Doug Cardwell commented "We've had more crime attributed to Straight Edge than any criminal street gang this year" and that "It's ironic and disappointing that otherwise good kids are committing crimes to promote their own personal philosophy." See the linked article for full details.