The Sixth Circuit Court of Appeals on November 6 upheld same-sex marriage bans in Ohio, Michigan, Kentucky, and Tennessee, making it the first federal appeals court in the country to come down against marriage equality since 2013.

Beyond stopping gay and lesbian couples from marrying in several states, the decision makes it very likely that the Supreme Court will now take up and rule on a same-sex marriage case. The nation's highest court previously side-stepped the debate, triggering a wave of lower court rulings in October that ended same-sex marriage bans in more than a dozen states. One Supreme Court justice said the court decided not to act because circuit courts had been in agreement at the time that states' same-sex marriage bans violate the Constitution's Equal Protection and Due Process Clauses.

"[W]hen there's no disagreement among the courts of appeals, we don't step in," Justice Ruth Bader Ginsburg said at the 92nd Street Y event on October 19. "The major job that the court has is to keep the law of the United States more or less uniform. So when courts of appeals disagree about what the law of the United States is, then we are obligated to grant review. If there had been a court of appeals on the other side, we probably would have taken that case."

The Sixth Circuit Court's decision puts it at odds with other federal appeals courts, making it almost certain, based on Ginsburg's rationale, that the Supreme Court will step in to settle the issue of same-sex marriage.

How is the Supreme Court expected to rule?

Following the Supreme Court's decision to strike down the federal ban on same-sex marriages, LGBT advocates are fairly confident that the court will rule 5-4 in favor of same-sex marriage rights across the country, based on constitutional rights set by the Fourteenth Amendment's Due Process and Equal Protection Clauses.

Justice Anthony Kennedy, who's expected to act as the fifth vote that decides the issue, wrote the majority opinion that struck down the federal ban on same-sex marriages with a legal rationale that could apply to states' bans. He argued that the federal ban violated constitutional protections and discriminated against same-sex couples by preventing them from fully accessing "laws pertaining to Social Security, housing, taxes, criminal sanctions, copyright, and veterans' benefits."

Since a similar legal argument applies to state-level programs and benefits attached to marriage, many court watchers expect Kennedy to rule against states' same-sex marriage bans as well.

Opponents of same-sex marriage rights argue the Supreme Court will allow states' bans to stand to protect states' rights. "The US Supreme Court has determined that states have the right to define marriage and we remain confident that they will uphold all the various traditional marriage laws and constitutional amendments that have been wrongly invalidated by federal judges," said Brian Brown, president of the National Organization for Marriage, in a statement. "We look forward to the US Supreme Court taking one or more of the … marriage cases now pending before them, and ultimately ruling that defining marriage as the union of one man and one woman is entirely constitutional."

But there is a precedent for the Supreme Court not allowing states to define marriage when it violates a person's constitutional rights. In Loving v. Virginia in 1967, the Supreme Court deemed states' bans on interracial marriage unconstitutional. "This case presents a constitutional question never addressed by this Court: whether a statutory scheme adopted by the State of Virginia to prevent marriages between persons solely on the basis of racial classifications violates the Equal Protection and Due Process Clauses of the Fourteenth Amendment," wrote Chief Justice Earl Warren. "For reasons which seem to us to reflect the central meaning of those constitutional commands, we conclude that these statutes cannot stand consistently with the Fourteenth Amendment."