I have received numerous calls from people who were married in DC and are in a same-sex marriage, but, neither party currently lives in DC.
In order to file for divorce in DC the requirements are the same for any divorce:
One of the parties must have been a resident of DC for at least six months prior to filing for divorce and you must be separated at least six-months mutually and voluntarily or for one year if the separation was not mutual and voluntary
It is always best to speak with a family law attorney so you know exactly what is required.