DENVER (AP) A federal appeals court ruled Tuesday that a Colorado law raising the age to purchase a gun from 18 to 21 can take effect while the legal battle over it continues.The 10th Circuit Court of Appeals said that lawyers for one of the young men who challenged the law with a gun rights group, Rocky Mountain Gun Owners, did not meet the legal burden for having the law blocked while the lawsuit played out. It sent the case back to a lower court for further proceedings.The law was one of four gun control bills signed by Democratic Gov. Jared Polis in 2023 following the lead of other states trying to confront a surge in violent crime and mass shootings.U.S. District Judge Philip Brimmer issued a preliminary injunction against it before it could take effect. His ruling frequently referenced a U.S. Supreme Court ruling that expanded Second Amendment rights, and concluded that the lawsuit would likely succeed. That 2022 Supreme Court decision in a New York case changed a test lower courts had used for evaluating challenges to gun laws.Colorados law effectively sought to prevent those between 18 and 20 from buying rifles and shotguns. A federal law already prevents licensed firearms dealers from selling handguns to those under 21 but that ban has also been challenged in light of the Supreme Court decision.A Polis spokesperson, Shelby Wieman, said in a statement that the law was commonsense gun safety legislation.The executive director of Rocky Mountain Gun Owners, Ian Escalante, did not immediately have a comment on the ruling.RELATED: Colorado lawmakers unveil series of bills to add more regulations around purchasing, possession of firearms (February 2023) Colorado governor signs 4 gun control laws months after deadly mass shooting in Colorado Springs (April 2023) Federal judge blocks age limit law on Colorado gun purchases (August 2023)