WASHINGTON — The Supreme Court is inappropriately signaling it intends to clear the way for gay marriage across the nation, Justice Clarence Thomas complained Monday in a stinging dissent to the court’s refusal to block the start of same-sex marriages in Alabama.

Bitterly objecting to Monday’s action, Thomas provided a rare insider’s perspective on the widely held view that the court’s embrace of gay marriage is a done deal.

Thomas filed a dissenting opinion after his colleagues rejected Alabama’s plea to put a hold on same-sex marriages in the state until the Supreme Court resolves the issue nationwide in a few months.

He criticized his fellow justices for looking “the other way as yet another federal district judge casts aside state laws,” rather than following the customary course of leaving those laws in place until the court answers an important constitutional question.

“This acquiescence may well be seen as a signal of the court’s intended resolution of that question,” Thomas wrote in an opinion that was joined by Justice Antonin Scalia. “This is not the proper way” for the court to carry out its role under the Constitution, he wrote, “and, it is indecorous for this court to pretend that it is.”

The opinion was remarkable less for the legal result it suggested than for its open criticism of fellow justices. After all, many legal commentators have predicted not only the case’s outcome this spring (in favor of same-sex marriage), but the vote (5-4) and the author of the majority opinion (Justice Anthony Kennedy).

The number of states in which gay and lesbian couples can marry has nearly doubled since October, from 19 to 37, largely as a result of terse Supreme Court orders that allowed lower court rulings to become final and rejected state efforts to keep marriage bans in place pending appeals.

“If you read the tea leaves the Supreme Court is leaving, the bans on same-sex marriage can’t be permitted. They’re unconstitutional,” said University of California-Berkeley law professor Jesse Choper.

Alabama became the 37th state in which same-sex couples can marry, following U.S. District Judge Callie Granade’s ruling in January that struck down as unconstitutional the state’s statutory and constitutional bans.

Granade had put her order on hold until Monday to let the state prepare for the change, and State Attorney General Luther Strange had asked for the delay to be extended for at least a few months.

Monday morning, probate judges in Alabama began issuing marriage licenses to same-sex couples, some of whom had been lined up for hours. “It’s about time,” said Shante Wolfe, 21, as she left the courthouse in Montgomery with wife Tori Sisson. They had camped out in a blue and white tent to be the first in the county given a license.