This past spring, strangely similar pieces of mail started arriving at the offices of city attorneys in 28 Maryland communities. The tersely worded letters, many dated March 26, warned each town that some of its firearms laws were illegal and needed to be repealed immediately. Takoma Park's letter claimed that ordinances against carrying unlocked guns and possessing or selling guns in public places "grossly" exceeded state law and should be taken off the books, "out of respect for the rule of law." All of the letters warned that failure to comply would put the towns "at risk for a lawsuit."

"Once in a blue moon we get these kinds of letters from activist organizations," says Ryan Spiegel, vice president of the Montgomery County chapter of the Maryland Municipal League and a member of the Gaithersburg city council. What felt different this time, he says, was the coordination—and the timing: Just a month earlier, the Maryland Senate had passed some of the country's toughest gun control measures in the wake of the Sandy Hook Elementary School massacre.

The letters came from the Second Amendment Foundation, a prominent pro-gun legal-defense organization, as part of a quiet but mounting campaign to strike down local gun laws across the country. So far, SAF has sent out about 425 letters to cities, towns, and counties in Maryland, Oregon, Virginia, and Washington and has announced plans to target hundreds more local laws.

Though they may be obscure and not always enforced, local gun laws have become low-hanging fruit for anti-gun-control activists since Sandy Hook. The strategy rests on the legal concept of "preemption," which restricts local lawmakers' authority to regulate firearms beyond what's in state law. For more than 30 years, the National Rifle Association and other pro-gun groups have successfully lobbied for preemption laws nationwide: In 1979, 7 states had them, but today, 45 do. Some states, such as Alabama, Idaho, and Maine, make exceptions for local restrictions on when and where people can shoot; some, like California, let localities control where and how guns are sold. All of them, however, set some limits to municipalities' ability to regulate guns, and that's where the Second Amendment Foundation comes in.

http://www.motherjones.com/politics/2013/12/gun-laws-second-amendment-foundation