That’s going to be arguable. DC isn’t a state, and I’d think that’s going to make trying to use this as precedent a messy proposition.
That's a red herring brought up by the District of Columbia. The 2nd Amendment applies to the federal government. The location of the individual is irrelevant. The feds can't violate the RKBA, Period. Also, the phrase "free State" is referring to a free society. An earlier draft of the Amendment referred to a "free country."