San Jose Mayor Sam Liccardo argued that gun owners must purchase liability insurance, but acknowledged that criminals will not follow along.

In an op-ed for the Washington Post, Liccardo pointed out that car owners need to buy liability insurance in order to drive and said the idea makes sense because "taxpayers have subsidized gun ownership and the harms that accompany it."

"Direct costs of gun violence to California taxpayers — for ambulances, cops and emergency rooms — exceeded $1.4 billion last year, according to one study. While the Second Amendment protects a right to bear arms, it does not require taxpayers to subsidize the exercise of that right," Liccardo wrote. "Courts routinely uphold the imposition of reasonable, nonobstructive fees or taxes on constitutionally protected activities, such as forming a tax-exempt nonprofit, selling a newspaper and purchasing a gun."

The Democratic mayor goes on to note one of the problems with his proposal. "Of course, 'the crooks' won’t pay a fee or buy insurance; only law-abiding gun owners would. An insurance requirement at the point of sale, if purchased locally, would make it harder for some guns to get into the wrong hands."

Despite the drawback, Liccardo said requiring liability insurance for guns could be a useful tool for police when searching suspects, since having an uninsured gun would be charged similarly to a driver using an uninsured vehicle.

"If some gun owners can’t get insurance, then our proposal simply requires them to pay an annual fee to compensate taxpayers who have grudgingly borne the financial costs of gun violence," he wrote.

Mandating liability insurance for gun owners has been floated by at least one of the Democratic presidential candidates, California Rep. Eric Swalwell. He has since dropped out of the race, though part of his extensive plan included having gun owners purchase it before being able to buy or trade firearms.