The theft of copper wiring stripped from irrigation pumps and other machinery -- including an electrical generator that, when damaged, caused an explosion that shut down portions of the UC Berkeley campus this week -- continues to be an expensive and perplexing problem across the nation.

The Legislature passed four laws last year designed to make it tougher for thieves to sell stolen metal. Among the many new rules: Sellers must wait three days before receiving payment and provide an ID and thumb print.

When Gov. Jerry Brown got around to considering a fifth scrap metal bill, AB 841, which would have required that sellers accept payment only by way of a mailed check, he was understandably fatigued. "How much more do you need?" he wrote in his veto statement.

The aggressive enforcement of existing laws ought to be enough to make a dent in this frustrating problem. At some point, scrap metal dealers should be able to make a living without being overwhelmed by regulation.