RICHMOND, Va. — Virginia’s same-sex marriage ban is unconstitutional, a federal appeals court ruled Monday in a decision that could overturn similar prohibitions in the Carolinas and West Virginia.

The 4th U.S. Circuit Court of Appeals in Richmond is the second federal appellate court to overturn gay marriage bans, after the Denver circuit, and its ruling is the first to affect the South, where states’ rights have held particular sway for generations.

In Monday’s 2-1 opinion, the judges ruled that Virginia’s constitutional and statutory provisions barring gay marriage and denying recognition of such unions performed in other states violate the U.S. Constitution. The defendants are likely to ask for the ruling to be stayed pending more appeals to the full 4th circuit and the U.S. Supreme Court; otherwise, marriage licenses to same-sex couples could begin being issued in 21 days.

Virginians voted 57 percent to 43 percent in 2006 to amend their constitution to ban gay marriage. Virginia laws also prohibit recognizing same-sex marriages performed in other states.

Writing for the 2-1 majority, Judge Henry F. Floyd said Virginia’s bans “impermissibly infringe on its citizens’ fundamental right to marry.”

“We recognize that same-sex marriage makes some people deeply uncomfortable. However, inertia and apprehension are not legitimate bases for denying same-sex couples due process and equal protection of the laws,” Floyd wrote, joined by Judge Roger L. Gregory. Judge Paul V. Niemeyer dissented.

Gay marriage proponents have won more than 20 legal decisions around the country since the U.S. Supreme Court struck down part of the federal Defense of Marriage Act last year. Most are still under appeal. More than 70 cases have been filed in all 31 states that prohibit same-sex marriage. Nineteen states, including Maine, and the District of Columbia allow such marriages.

The many rulings give the U.S. Supreme Court plenty of options to take up gay marriage again in its next term, starting in October.

The 4th Circuit decision also will apply to other states in the circuit when the decision becomes final in 21 days, providing that the court does not issue a stay if requested, said James Esseks, an attorney with the American Civil Liberties Union. Maryland, one of the states in the circuit, already allows same-sex marriages.