Trigger-lock law threatened
A separate ordinance, passed by the Board of Supervisors in 2007, requires gun-owning residents to keep their weapons in locked boxes or to disable them with trigger locks. Cox said the NRA might challenge that law as well.

The District of Columbia had a similar provision in its 32-year-old handgun ordinance that the Supreme Court overturned Thursday. In addition to prohibiting residents from carrying guns, the ordinance required owners to keep their weapons locked up or inoperable in their homes.

That restriction, the court said, "makes it impossible for citizens to use them for the core lawful purpose of self-defense." One advantage of having a loaded handgun available, Scalia observed, is that "it can be pointed at a burglar with one hand while the other hand dials the police."

San Francisco District Attorney Kamala Harris said both the Housing Authority ban and the local trigger-lock requirement appear to be vulnerable under the ruling.

The ruling "leaves open for dispute and interpretation some of the existing laws that we have restricting or regulating gun ownership and use," said Harris, who was co-author of a brief signed by 18 prosecutors around the nation urging the court to rule narrowly and leave local regulations intact.

"At the very least, it's going to clog up our courts," Harris said of the decision.

San Francisco