Stop in for a cup of coffee

Pot is legal in DC? It's illegal federally! How does that work?
Oops, getting political . Sorry lol
DC is not a state and not under General federal jurisdiction either. It is an odd little island of ambiguity within the US laws. It is simply a “District” governed by Congress and falls outside the rest of the laws governing states and Federal territories. This helps a little to understand it.

The signing of the Residence Act on July 16, 1790, approved the creation of a capital district located along the Potomac River on the country's East Coast. The U.S. Constitution provided for a federal district under the exclusive jurisdiction of the U.S. Congress, otherwise know as the District of Columbia.