Agreed. Smoking in public and outside is technically illegal. Though DC and the mayor, and the council have decided NOT to enforce the laws and turn a blind eye. Had I known that, I NEVER would have voted for legalization. Now, on the ballot is Initiative 81, for legalization of hallucinogenics. Thought they way the ballot is written, it seems like a positive thing. After witnessing a tripping man having sex with our retaining wall, and the ever present drugs of all kind in DC, we are voting against Initiative 81. I urge everyone to do the same.
As for your neighbors, you are legally able to enjoy your property. If the neighbors are doing something that prevents your from enjoying your property, then you can force them to stop. Sending a letter to landlord is a good first step. Talking to them is a good second step.
Problem is that most people are completely clueless about the laws in DC, as can be seen by some of the responses in this thread. People think that smoking in public is permitted but it is not. There needs to be a movement to push back again the drug users as their lobby and misinformation has gotten so strong that you can't say anything against pot before getting attacked.
This is not really the environment we want to raise our children. The Mayor and Council are eyeing the future tax revues of the legalization of drugs. The rest of us can just move out if we don't want to smell the stench all day and night.