A federal court has dealt a blow to gun rights groups by ruling Gov. Phil Murphy's ban on 15-round magazines doesn't violate the Constitution.

The group that challenged the 10-round magazine limit on firearms in the state already filed their appeal Monday night and vowed to fight the law to the Supreme Court.

The group, the Association of New Jersey Rifle and Pistol Clubs, challenged the new law in court within an hour after Murphy signed the legislation in June. The measure gives gun owners until early December to sell, modify, destroy or turn over to the police their any gun magazines that can hold more than 10 rounds.

"It turns a million people into criminals with the stroke of a pen," Scott Bach, the group's executive director, said Monday night.

New Jersey State Police State does not say how many gun permits there are in the state. But groups like Bach's estimate there are 1 million people in the state who own firearms."

The state argued the new law could mitigate death tolls in mass shootings.

The U.S. District Court, in a ruling handed down late Friday, said New Jersey's law doesn't "prevent ownership of any type of gun and does not restrict the quantity of ammunition a gun owner may possess." Rather, it "merely restricts the quantity of bullets a magazine may hold."

The decision continues: "To illustrate, a citizen who owns a gun, 30 rounds of ammunition, and two 15-round magazines prior to the (new law's) enactment will be permitted to retain his gun, ammunition, and three 10-round magazines."

Eight other states and the District of Columbia have enacted laws that put restrictions on magazine capacity: California, Colorado, Connecticut, Hawaii, Maryland, Massachusetts, New York, and Vermont.

Murphy signed the bill into law on June 13. It gives gun owners a six-month grace period to get rid of or modify their magazines.

State Attorney General Gurbir Grewal hailed the ruling in a tweet.

ICYMI: On Friday night, fed ct found that NJ’s ban on large capacity magazines is constitutional. Big win for public safety! https://t.co/DTDMgZRxho pic.twitter.com/70NGaBdHmy — AG Gurbir Grewal (@NewJerseyOAG) October 1, 2018

The Association of New Jersey Rifle and Pistol Clubs appealed the ruling to Third Circuit Court.

Matt Arco may be reached at marco@njadvancemedia.com. Follow him on Twitter @MatthewArco or Facebook.