Legal departments in fear of government regulators used to peer over their shoulders at a fairly predictable lot of state and federal agencies poised to pounce.

But increasingly general counsel cower under a much broader, multifaceted threat: state attorneys general in the 50 states, the District of Columbia and U.S. territories. Striking alone or increasingly teaming up with other states to pool their resources, they punch above their weight—sometimes even with federal agencies in tow.