The Supreme Court is set to hear historic arguments in cases that could make same-sex marriage the law of the land.



The justices are meeting Tuesday to offer the first public indication of where they stand in the dispute over whether states can continue defining marriage as the union of a man and a woman, or whether the Constitution gives gay and lesbian couples the right to marry.



The court is hearing extended arguments, which also will explore whether states that do not permit same-sex marriage must nonetheless recognize such unions from elsewhere.



Same-sex couples can marry in 36 states and the District of Columbia.



The cases before the court come from Kentucky, Michigan, Ohio and Tennessee, four of the 14 remaining states that allow only heterosexual marriage. Those four states had their marriage bans upheld by the federal appeals court in Cincinnati in November. That is the only federal appeals court that has ruled in favor of the states since the Supreme Court in 2013 struck down part of the federal anti-gay marriage law.



Justice Anthony Kennedy has written the court's three prior gay rights decisions, including the case from two years ago. All eyes will be on Kennedy for any signals that he is prepared to take the final step in granting marriage rights to same-sex couples.



Such an outcome was inconceivable just a few years ago.



The first state to allow gay and lesbian couples to marry was Massachusetts, in 2004. Even as recently as October, barely a third of the states permitted it. Now, same-sex couples can marry in 36 states and the District of Columbia, a dramatic change in the law that has been accompanied by an equally fast shift in public opinion.



The main thrust of the states' case is to reframe the debate.



"This case is not about the best marriage definition. It is about the fundamental question regarding how our democracy resolves such debates about social policy: Who decides, the people of each state or the federal judiciary?'' John Bursch, representing Michigan, wrote in his main brief to the court.



Other arguments by the states and more than five-dozen briefs by their defenders warn the justices of harms that could result "if you remove the man-woman definition and replace it with the genderless any-two-persons definition,'' said Gene Schaerr, a Washington lawyer.



The push for same-sex marriage comes down to fairness, said Mary Bonauto, who will argue on behalf of the plaintiffs. The people who have brought their cases to the Supreme Court are "real people who are deeply committed to each other. Yet they are foreclosed from making that commitment simply because of who they are,'' she told reporters last week.



Arguments made by Bonauto, other lawyers for same-sex couples and more than six-dozen supporting briefs have strong echoes of the 1967 Loving v. Virginia case, in which the Supreme Court struck down state bans on interracial marriage. In that case, the justices were unanimous that those bans violated the constitutional rights of interracial couples.



No one expects unanimity this time. But many believe the justices will take the final step toward what gay rights supporters call marriage equality, in part because they allowed orders in favor of same-sex couples to take effect even as the issue made its way through the federal court system.



That was action through inaction, as other judges played a major role over the years. Only 11 states have granted marriage rights to same-sex couples through the ballot or the legislature. Court rulings are responsible for all the others.



A decision is expected in late June.