FILE - In this May 3, 2013, file photo, U.S. Attorney Mike Cotter discusses the end of a three-year investigation into Montana medical marijuana in a news conference in Helena, Mont. With the number of registered pot providers in the state topping 4,800, with billboard ads and huge greenhouses operating in the open, the feds stepped in with a series of raids across the state in 2011, leading to convictions of 33 providers and, coupled with a major rewrite of the state law, the demise of most commercial sales. (AP Photo/Matt Volz)