SUNNYVALE -- Sunnyvale's new gun-control ordinance stops at the city line, but the National Rifle Association hopes a federal lawsuit it filed this week challenging the law will ripple all the way to the U.S. Supreme Court.

The gun rights group's highly anticipated suit comes six weeks after 67 percent of Sunnyvale voters approved the ordinance as Measure C. The NRA took aim at part of the ordinance that requires owners of magazines that hold more than 10 rounds of ammunition to remove them from the city, sell them outside California or to a licensed gun dealer, or give them up to police for destruction within 90 days.

Measure C took effect Dec. 6, giving owners until March 6 to comply. But the lawsuit filed Monday -- in which the NRA is backing five Sunnyvale residents who own such magazines -- seeks an injunction halting enforcement of the new law, claiming it impinges upon their Second Amendment right to self-defense.

It's the second lawsuit to challenge the ordinance in as many weeks, and the start of a long fight here and part of a broader policy war nationwide.

"There's an epic legal battle for the future of the Second Amendment going on across the nation right now, and Sunnyvale, by passing this ordinance, jumped right into the middle of the fray," said Chuck Michel, the NRA's West Coast counsel. This case "really is, in many ways, perfect for Supreme Court review."

Sunnyvale Mayor Tony Spitaleri, who pushed for Measure C and is among this lawsuit's defendants, says he's surprised the NRA -- which had threatened to sue even before the measure passed -- took so long to act.

"Any law that deals with safety or guns, they will oppose, no matter what it is," he said. "The claims they're making, as far as I'm concerned, don't hold any water."

The lawsuit claims magazines holding more than 10 rounds are standard equipment for many popular pistols and rifles; in fact, most pistols sold in the U.S. are made and sold with magazines holding between 10 and 17 rounds. Limiting Sunnyvale residents to reduced-capacity magazines limits their ability to defend themselves, the suit says, giving criminals an advantage.

"If someone is breaking into your house, they are on the offensive, they have the opportunity to prepare," Michel said, but a law-abiding gun owner -- who must keep their gun locked up under another section of Measure C -- will have only seconds to react.

"If you have to pull the trigger, odds are in a situation like that you're going to miss a few," he said. "Having the extra rounds in that magazine can be the difference between life and death when you're defending yourself and your family."

But state law has banned the purchase of magazines holding more than 10 rounds since 2000, and only those who owned them before that time were allowed to keep them. "So then why shouldn't it be against the law to have them in your possession?" Spitaleri asked rhetorically.

Measure C's other sections require gun owners to notify police within 48 hours of the loss or theft of a firearm and keep firearms locked up when not in the owner's immediate possession, and require ammunition sellers to log and keep buyers' names for two years.

A Santa Clara County Superior Court lawsuit filed last week by Sunnyvale gun store U.S. Firearms; its owner, Eric Fisher; and the National Shooting Sports Foundation, a gun-industry trade group, claims the ammo sales provision is pre-empted by state law and illegally shares customers' data with police, and that the loss or theft reporting provision conflicts with state and federal laws.

Sunnyvale announced last week that the San Francisco law firm of Farella Braun + Martel will represent the city for free to defend the ordinance against all challenges.

Josh Richman covers politics. Contact him at 510-208-6428. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.