A long standing legal prohibition on federal enforcement against state legal medical cannabis operators expired on December 21, 2018 when the U.S. Government partially shut down. The amendment had been renewed and extended multiple times through that date.
First adopted in 2014, the amendment to annual appropriations bills known as the Rohrabacher-Blumenauer Amendment is expected to be reimplemented when the Government is reopened and the current budget stalemate resolved. In the meantime, however, technically, federal enforcement against state legal medical cannabis companies is possible. That said, most of the government agencies who could pursue such enforcement remain unfunded and shut down.
Most commentators also do not expect to see any change in federal enforcement activity as public sentiment, Congressional activity and state legalization efforts are all moving in the direction of ultimately eliminating prohibition on the medical and adult use of cannabis.