It's easy for Congress to meddle with the District of Columbia's decision to legalize recreational use of marijuana, but taking on the states is a different matter.
Congress has passed a spending bill that prevents the District from using federal money to enact any law or regulation that repeals or reduces marijuana-related penalties. The action is in direct response to a voter initiative passed last month that allows possession of small amounts of marijuana.
The Constitution gives Congress the power to review and possibly reject all legislation approved by the District's elected officials or its citizens.
Analysts say Congress has less leverage with the states, and thwarting efforts supported by a plurality of voters back home could prove politically risky at election time.