This is not a positive step at all. DC is a crowded city swarming with cops, it's insane to carry a gun for self-defense. Maybe a few people will walk around strapped because they're scared of black people or whatever. But, mostly this will have no effect on law-abiding citizens.
The actual problem could for the police. Imagine they've searched a suspect and they find an illegal gun. He can claim it's a legal gun and perhaps they'll be forced to allow someone to go free and murder someone. It could also interfere with police using an illegal gun charge to get someone off the streets so they can obtain warrants or prevent imminent violence.
Er I doubt police use the honor system to determine if a gun is legally held or not.
