Since DC is not a state, it has no legal standing to challenge a handgun ban. Even if it were a state, the handgun ban should be supported. DC is an extremely violent region, and handguns only have one practical purpose: to kill human beings. Handguns are more likely to kill their owners than other people, and they are a dangerous public nuisance.
Washington D.C. had a ban on handguns in the city limits that was struck down in 2008 by the Supreme Court. Even though Washington D.C. is not a state it is part of the United States of America. The 2nd Amendment applies to the entirety of the United States and the Supreme Court correctly ruled that it applies in D.C.