A federal appeals court panel struck down the law in March, rejecting the city's argument that the Second Amendment right to bear arms applied only to militias. The full appeals court refused to reconsider the decision in May. The law has remained in effect during the appeals process.
"We have made the determination that this law can and should be defended," Mayor Adrian M. Fenty said in a statement Monday.
Washington's gun law dating to 1976 bars residents from keeping handguns in their homes and prohibits the carrying of a gun without a license. Registered firearms must be kept unloaded and disassembled. The city's sweeping gun ban is matched only by Chicago among large U.S. cities.
If the high court takes up the case, it would mark the first time in 70 years that justices will consider the breadth of the Second Amendment. In 2003, the court chose not to take a case that challenged California's ban on assault weapons.
D.C. officials say the laws are needed in a city that has been plagued by high homicide rates. But opponents of the law, including the National Rifle Association, argue the laws strip citizens of the right to protect themselves against crime.