Last year, the number of gun stores burglarized in the United States rose to record-breaking levels as growing ranks of criminals used the crudest smash-and-grab methods to break into firearms dealers and make off with weapons. The number of burglaries reported to the Bureau of Alcohol, Tobacco, Firearms and Explosives shot up 30 percent to 558, the highest level on record.

While the trend was mostly concentrated in Southern states like Texas, Georgia, Florida and the Carolinas, where dealers are subject to no minimum security requirements, the crime wave also extended to California, which already required dealers to keep guns on their business premises either locked individually in display cases or stored in a fireproof safe.

According to the ATF, 30 stores in California reported a burglary in 2016 — more than twice as many as the year before, and three times the total from 2012, the earliest year for which data is available.

Despite the rise in burglaries, Governor Jerry Brown on Friday vetoed a bill that would have strengthened California’s requirements for gun-store security measures.

The legislation had passed both the state Assembly and Senate by nearly two-to-one margins. In a statement announcing his veto, Brown indicated that he viewed the proposed mandates as unnecessary, noting that many localities already have tougher security measures than required by state law, and that gun stores often undertake their own additional measures to prevent theft.

Even with those security features in place throughout the state, however, thieves in California are still regularly tempted by gun stores. In March 2016, thieves using a stolen car rammed their way into a dealer in Petaluma that had been equipped with a grate across its front door. That May, a store in Rocklin that was the target of another smash-and-grab theft was hit for 100 guns.

The California bill was written with heists like those in mind. Had it been signed, gun dealers who lock weapons after hours in display cases would have had to install bollards (short metal or concrete posts) in front of entrances or full-length windows to prevent cars from ramming into their stores, a common technique used in gun-store thefts around the country. Dealers who store weapons after hours in a safe would have had to ensure that they met durability standards set by the state attorney general.

Pro-gun activists in California had argued that the additional costs imposed by the legislation would have been “disastrous” for local gun businesses, predicting that many would be put out of business.

In its Bullet Points newsletter, the National Shooting Sports Foundation trade group applauded its California members for demanding that Brown veto the bill. Later in the same email, the group urged members to consult its guide on securing gun stores against burglaries.

“The more secure your building or site is and the better it is designed to withstand an attack, the greater the odds are that the building will not be breached by bad guys intent on stealing firearms they cannot otherwise legally obtain,” it reads.