The U.S. Supreme Court on Monday rejected a challenge by gun rights activists to a San Francisco regulation that requires gun owners to keep their weapons locked up or disabled when stored at home.

By declining to hear an appeal filed by gun owners and the National Rifle Association, the court left intact a March 2014 ruling by the San Francisco-based 9th U.S. Circuit Court of Appeals that upheld the measure.

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The regulation, issued in 2007, states that anyone who keeps a handgun at home must either store it in a locked container or disable it with a trigger lock.

The challengers said the regulation violates the U.S. Constitution’s Second Amendment, which guarantees the right to bear arms.

Two of the nine-justice court’s conservative justices, Clarence Thomas and Antonin Scalia, said they would have taken the case.

Thomas wrote that the Supreme Court has outlined to lower courts how to approach Second Amendment cases but the courts that oversaw the San Francisco case “have failed to protect it.”

In 2012, the gun owners unsuccessfully sought an injunction that would have prevented the regulation from being enforced.

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The appeals court also had upheld a regulation banning hollow-point ammunition that is designed to expand or fragment on impact, but that was not at issue in this appeal.

The Supreme Court has not taken up a major gun case since 2010. In the 2008 District of Columbia v. Heller case, the court held that the Second Amendment guaranteed an individual right to bear arms. Two years later in the case McDonald v. City of Chicago, the court held that the earlier ruling applied to the states.

As part of the 2008 ruling, the court struck down the District of Columbia’s trigger-lock requirement.

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The case on which the court acted on Monday is Jackson v. San Francisco, U.S. Supreme Court, No. 14-704.