The Supreme Court declined to hear a case involving a San Francisco ordinance that forces gun owners to keep a trigger lock on their guns, or lock them up at home when they are not being carried.

USA Today:

The city noted in its brief opposing the high court's review that "long" guns are not restricted and handguns can be kept loaded. It said keeping them locked up "reduces the risk of suicide and unintentional shootings, particularly among children and
teens," as well as making guns harder to steal.

A group of city residents who filed the suit, along with the National Rifle Association, argued that the law renders gun ownership self-defeating by making the gun inoperable when an intruder bursts on the scene. The high court's 5-4 majority in Heller struck down the District of Columbia's trigger-lock requirement.

"San Francisco has no more right than the District of Columbia to force its residents to fiddle with lock boxes or fumble with trigger locks when the need to use a handgun for immediate self-defense arises," the challengers argued in their brief seeking Supreme Court review.

A coalition of 25 states sided with the city residents in urging the court to overturn the law. Otherwise, they said, "responsible citizens will be unable to possess operable firearms in defense of hearth and home."

That was at the heart of the Thomas-Scalia dissent.

"The law ... burdens their right to self-defense at the times they are most vulnerable -- when they are sleeping, bathing, changing clothes, or otherwise indisposed," Thomas wrote. "There is consequently no question that San Francisco's law burdens the core of the Second Amendment right."

What makes this law truly bizarre is that one of the only ways it can be applied is in the aftermath of a home invasion where the resident used his gun for self-defense.  If there's no trigger lock or lock box, the resident may very well be arrested for defending himself.

When it comes to gun laws, common sense is usually thrown under the bus.  The standard in the past has been that gun rights can be restricted if there is a compelling public safety issue involved.  Sounds to me like the San Francisco law is a criminal safety issue – making sure that those who choose to arm themselves at home pose no danger to home invaders seeking to take lives or property.