Correct you are, and that argument itself MIGHT be grounds for overturning the handgun ban, which was passed by the "Washington DC city council", and NOT, I believe, by the Congress of the United States. One could argue that only Congress has the power/authority to implement such a ban.
I discontinued my membership to the NRA several years because of their propensity to negotiate and legislate State and Federal "gun privleges" as opposed to litigation on hard core consitutional principles.
Some of the battles they've "won" only serve to enhance the Govt's perceived validity to create unconstitutional laws in the first place.
Sui