The Seattle City Council passed a new tax on guns and ammunition Monday to raise revenue for violence prevention and gun safety research.

The council unanimously approved the measure, adding a $25 tax on firearms sold in the city and a 5-cent tax on each round of ammunition. The legislation also requires gun owners to report lost or stolen firearms within 24 hours.

Council President Tim Burgess noted that a Seattle hospital treated 253 shooting victims last year, costing taxpayers more than $12 million. Lawmakers plan to use the estimated $500,000 the tax would generate annually to offset the costs linked to gun violence and to fund anti-violence programs.

“Every day, the general public pays the enormous cost of gun violence,” Burgess said. “Gun violence is a public health crisis in our city and our nation. City government can and must pursue innovative gun safety measures that save lives and save money.”

Opponents argue that the measure will push gun shops out of Seattle and have threatened to sue, claiming that the city does not have the authority to enforce the measure.

Washington state bars local governments from imposing laws related to firearms unless explicitly authorized by the state.

The NRA’s lobbying arm, the Institute for Legislative Action, said the tax violates state law and hurts low-income people who are more likely to live in areas with higher crime.

“The burden of regressive taxes like the Seattle proposal falls squarely on those that are least able to afford them,” the Institute for Legislative Action wrote in a statement. “Persons of means will simply drive outside the city to purchase firearms and ammunition, while those without such options will be forced to go forego [sic] their rights or pay the tax.”

Sergey Solyanik, the owner of a Seattle gun shop, levied a similar argument before the council, contending that the tax would divert customers to nearby cities to purchase guns at a lower price, forcing him to close his store.

“The only real purpose of this legislation is to run gun stores out of Seattle,” he said.

Solyanik predicted that gun store owners would file a lawsuit against the city, stalling and potentially killing the law’s implementation.

“It is extremely easy to show that the only intent with this law is not collecting the revenue, but legislating on guns, and it should be easy for a court to see that this is illegal,” he told a local CBS affiliate.