When it comes to legalization of same-sex marriage, the fight essentially is over. The only remaining question is how and when it will officially end.

And the answer may come not from Washington but from downtown New Orleans, not from the U.S. Supreme Court but from the notoriously conservative 5th Circuit Court of Appeals.

The high court’s decision earlier this week to leave in place three rulings from other appeals courts legalizing gay marriage — a move that sets up legalization in an astonishing 30 states — creates two likely scenarios.

Under the first, the Supreme Court will wait for one of the country’s 11 circuit courts to uphold a state ban, so that it can step in and settle the conflict. If that happens, the most likely outcome is an acknowledgement of the reality on the ground, the preponderance of judicial opinions that created that reality and rapidly solidifying public opinion in support of marriage equality.

Under the second, courts across the country will fall in line and keep invalidating state bans, until none are left standing. If that happens, same-sex marriage will become the law of the land without further action the court.

So far, the four appeals courts that have taken up the issue have agreed, including the San Francisco-based 9th Circuit, which struck down bans in Idaho and Nevada the day after the Supreme Court declined to review the other decisions, adding still more states to the legalization list. The 6th Circuit, in Ohio, has heard oral arguments, and handicappers say the three-judge panel there could go either way.

But it’s the 5th Circuit, which has jurisdiction over federal matters in Louisiana, Texas and Mississippi and which is staffed by judges from those states — several of whom have wound up on short lists of potential Supreme Court appointees for Republican presidents — that has long been considered most likely to go its own way. It’s the 5th Circuit that may be most inclined to uphold the states’ rights argument against striking down state bans and to look skeptically on the contention that gay marriage is essentially a civil right, guaranteed by the Constitution’s equal protection clause no matter what voters or lawmakers in individual states say. And so it’s the 5th Circuit that may well determine which scenario plays out.

Just about every federal judge across the land, at both the district and appellate level, has found marriage bans unconstitutional. The outlier, of course, is U.S. District Judge Martin Feldman, who in September upheld Louisiana’s decade-old same-sex marriage ban. The plaintiffs, a handful of Louisiana couples seeking to have their out-of-state marriages recognized and the gay-rights group Forum for Equality, are appealing and have brought in big-time support from the national group Lambda Legal.

The 5th Circuit, which also has a Texas case pending, has expedited the case. Briefs from the plaintiffs and the states are due Nov. 7, and a hearing should follow soon after.

So what to expect once that happens? A lot obviously depends on which judges are chosen to consider the matter, but one related case from a few years back provides a hint as to the court’s overall leanings. U.S. District Judge Jay Zainey had ruled that two New York men who’d adopted a child from Louisiana could get a birth certificate listing both as legal parents (in New York, unmarried couples can jointly adopt, but the practice is illegal in Louisiana). A three-judge panel from the 5th Circuit upheld his decision. But Attorney General Buddy Caldwell asked for a rehearing from the full appeals court, which proved eager to overturn the earlier ruling.

It hasn’t always been that way, though. Students of the court’s storied history know that several of its judges, including John Minor Wisdom, whose name graces the courthouse, were once at the forefront of expanding, not limiting, civil rights. In the years after the landmark Brown v. Board of Education decision, “The Four,” as they were known, issued important rulings giving African-Americans access to the ballot, the right to sit on juries and the ability to attend previously segregated colleges.

It took not just compassion but courage for that earlier generation of 5th Circuit judges to rule as they did. But they got what was at stake for the individuals involved and for the country, and they understood how history would judge their actions.

So maybe the real question is this: Do the judges on today’s 5th Circuit get that, too?

Stephanie Grace can be contacted at sgrace@theadvocate.com. Read her blog at http://blogs.theadvocate.com/gracenotes. Follow her on Twitter, @stephgracenola.