Associated Press/Keith Srakocic
Herb Belin, an exhibitor with Smith & Wesson, secures one of the .45 cal pistols at the display set up before the National Rifle Association\'s 140th annual meetings and exhibit, Thursday, April 28, 2011 in Pittsburgh. This month the NRA and other gun-rights groups are suing the city of Seattle over a controversial city gun law.

SEATTLE — Three gun-rights groups, including the National Rifle Association, are suing the city of Seattle over its adoption this month of a so-called "gun violence tax."

The NRA was joined by the National Shooting Sports Foundation and the Bellevue, Washington-based Second Amendment Foundation. The lawsuit, filed Monday in King County Superior Court, accuses the city of violating Washington state law, which prohibits local governments from adopting laws related to firearms unless those local ordinances are specifically authorized.

The tax amounts to $25 for each firearm sold in the city, plus 5 cents per round for nearly every type of ammunition. The revenue would be used for gun safety research and gun violence prevention programs.

City Attorney Pete Holmes has argued that the gun violence tax falls squarely under Seattle's taxing authority.