Montana has joined 30 other states in urging the U.S. Supreme Court to uphold a lower court ruling affirming the individual’s right to bear arms, state Attorney General Mike McGrath said Monday.

The states signed a ‘‘friend-of-the-court’’ brief that contends a federal appeals court was correct in finding the District of Columbia’s ban on handguns violated the Second Amendment of the U.S. Constitution.

The Second Amendment says: ‘‘A well-regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.’’

‘‘At issue here is whether the Second Amendment has any modern meaning and whether it allows individual citizens to have a weapon for private use,’’ McGrath said in a news release. ‘‘We believe it does, and that an outright ban like the one in D.C. is inconsistent with the Constitution.’’

The District of Columbia bans ownership of handguns and requires that other guns that are kept in homes be trigger-locked or taken apart.

McGrath said the Supreme Court will address whether the Constitution guarantees an individual right to have a gun for a private use, or whether it ensures only the collective right to have guns in organized military service.

The case — District of Columbia v. Heller — centers on Dick A. Heller, a security guard and D.C. resident who carries a gun while on the job. Heller applied for a permit to keep a handgun in his home and was turned down.

In March 2007, a federal appeals court found in his favor. The District of Columbia appealed, and in November, the U.S. Supreme Court agreed to hear the case.

The Texas attorney general’s office prepared the brief that was filed Monday, and the case will be argued March 18, the release said.

Bipartisan majorities in Congress also are backing gun owners in challenging the District of Columbia handgun ban. Last week 55 senators and 250 representatives signed a brief urging the high court to strike down the ban.

Among them were Democratic Sens. Jon Tester and Max Baucus and Republican Rep. Denny Rehberg.