If there is going to be a solution to the problem of mass gun violence in America, it is going to have to come from the federal government. The states cannot save us, no matter how nobly they try.

That seems to be the prime policy lesson of the mass shooting horror that took place Sunday at the Gilroy Garlic Festival in California. A 19-year-old man besotted with white supremacy and armed with an assault rifle opened fire, killing three people — including a 6-year-old boy and a 13-year-old girl.

California has some of the strictest gun laws in the nation — including an assault weapons ban — but that didn't matter. Just weeks before Sunday's massacre, the shooter bought his semiautomatic rifle in neighboring Nevada, where the gun remains legal. A 2017 study revealed that, in the weeks after gun shows are held in Nevada, gun-related deaths and injuries in California jump 70 percent.

That isn't a problem California can solve on its own.

Anti-violence activists have spent the last couple of years trying to circumvent the National Rifle Association and its allies on Capitol Hill by taking their case to state legislatures instead. And they've been remarkably effective: New laws in California, Illinois, Oregon, and Washington state, for example, have placed new barriers on gun ownership — raising the minimum age to buy firearms, taking guns from people deemed a threat to themselves or others, banning domestic abusers from owning guns, and expanding firearms checks.

That's good news. For years, it seemed that Second Amendment fundamentalists had a lock on governance at both the state and federal levels. Now anti-gun activists have started to find traction. But the killings in Gilroy show that state-level action is not enough on its own.

That was foreseeable. There are not walls around our states and cities, so it has always been pretty easy to violate local gun laws by bringing firearms in from the outside. Gun-rights advocates have long pointed out that Chicago has one of the highest murder rates in the country despite Illinois' tough gun laws. But the city is within easy reach of two states with relatively lax gun laws, Indiana and Wisconsin. Similarly, studies have shown that most of the guns used in New York crimes come from out of state.

The feds have to get involved.

Getting federal action on gun control, though, remains a daunting project. Sen. Mitch McConnell (R-Ky.) still runs the Senate, after all, and it is seems impossible that he would let any significant gun legislation ever come to vote in the chamber — not that such legislation could ever win majority backing from Republicans, anyway. The increasing conservatism of the Supreme Court also looms as an obstacle.

But there are reasons to hope. For one thing, the NRA is at a remarkably weak point in its recent history. The organization is beset by infighting and questions about its finances. It is a less formidable opponent at this moment than it has been for the last generation or so. Will that make a difference? Pro-gun lawmakers will probably remain pro-gun — but the lobbying and contributions of the NRA likely stiffens their spines. If the organization slips, there could be an opening for anti-gun activists to pass legislation at the federal level.

Democrats also seem more willing to mount a fight on gun control issues. Both Barack Obama and Hillary Clinton made a public show of honoring rural hunting traditions during their presidential campaigns. This year's presidential candidates are more outspoken in their advocacy of gun control measures.

"Democrats today not only see the issue as important," Pacific Standard's Seth Masket observed earlier this year, "but as a potential election winner, and not a drag on a national ticket."

Success, if it comes, won't save Stephen Romero or Keyla Salazar, the children so brutally and unnecessarily killed in Gilroy, California. But gun massacres have plagued America for a generation now — in schools, churches, and nightclubs, at concerts and festivals. They are making it more and more difficult for Americans to safely experience community. And it's likely we haven't even really begun to reckon with the ongoing, unending costs of all that violence. State officials have led the way in pushing back. It's time, at long last, that our leaders at the federal level join them.