Demonstrators at the March for Our Lives in Seattle, Washington. Photo: Lindsey Wasson/Getty Images

On Election Day last week, voters in Washington state approved Initiative 1639, a sweeping ballot measure that stands to usher in some of the strictest gun control measures in the nation. And the vote wasn’t close, with 60 percent of voters casting their ballots in favor of I-1639. But the overwhelming public support has run up against a familiar foe for those on the side of gun control: the National Rifle Association.

On Thursday, the NRA and other gun rights groups sued to block I-1639, which bans the sale of semiautomatic rifles to anyone under 21 and any non-Washington resident. It also requires background checks and waiting periods for anyone buying semiautomatic rifles and puts in place safe storage requirements for all firearms.

In their lawsuit, the NRA and its compatriots take issue with two parts of I-1639. First, they say the increased minimum age for rifle sales violates the First, Second and Fourteenth Amendments of the U.S. Constitution, along with a portion of Washington’s constitution. The prohibition on sales to out-of-state residents violates the commerce clause, argue the plaintiffs, who include gun dealers and young people affected by the age limit. They aren’t arguing against the storage rules, or any other portion of I-1639, but have asked the courts to block the entire measure while it’s determined if the two offending portions can be separated from the rest.

“I-1639 violates the constitutional rights of law-abiding citizens and puts people at risk,” Chris Cox, executive director of the NRA’s Institute for Legislative Action, said in a statement. “This lawsuit is the first step in the fight to ensure that Washingtonians are free to exercise their fundamental right to self-defense.”

Gun rights groups previously sued in an attempt to keep I-1639 off of the ballot, but the state Supreme Court ruled that voters could decide the issue. After that loss, opponents made no secret of their intention to sue again if the measure succeeded.

Supporters of I-1639 call this latest lawsuit a desperate attempt by gun rights groups to prevent something that the public overwhelmingly favors. “We always expected the NRA or the gun lobby in general, to sue and try to stop I-1639,” Tallman Trask, spokesman for the group that sponsored the measure, told the Seattle Times, because they “can’t stop it at the ballot box.”