The U.S. Supreme Court announced Friday that it will hear appeals in four same-sex-marriage cases, virtually assuring that it will issue a landmark ruling by the end of June on one of the era’s most contentious and fastest-changing social issues.

In accepting the cases — from Kentucky, Michigan, Ohio and Tennessee — the stage is set for a final legal battle over whether denying gay couples the ability to legally wed is a violation of the U.S. Constitution. The justices are expected to hear oral arguments in April and to decide by the end of June whether every state and U.S. territory must issue marriage licenses to same-sex couples and recognize such marriages conducted elsewhere.

A decision in favor of equal marriage rights would take its place in the canon of pivotal cases involving human rights, from Brown v. Board of Education in 1952, which forced desegregation, to Loving v. Virginia, which struck down state laws prohibiting interracial marriages.

“What the Loving case did for interracial marriage, we’re hoping these cases will do for same-sex marriage,” said Dana Nessel, an attorney for suburban Detroit couple April DeBoer and Jane Rowse, whose case is now on the Supreme Court docket.

DeBoer v. Snyder, first filed in January 2012, originally sought to force Michigan to allow both women to be legal parents to their four adopted children. It was expanded later that year to demand the legal right to marry. The couple’s case — and similar ones around the nation — was bolstered in June 2013 when the Supreme Court struck down the 1996 Defense of Marriage Act, which prohibited the federal government from recognizing same-sex marriages. The 5-4 decision, written by Associate Justice Anthony Kennedy, asserted that discriminating against same-sex couples who wish to wed is a violation of the due process clause of the Fifth Amendment.

That ruling, in United States v. Windsor, kicked off a winning streak for same-sex marriage advocates through the courts, with dozens of federal district judges and three three-judge panels at federal appellate courts concluding that states may not discriminate either. The number of states where gay couples can legally marry climbed from nine to 36 as of Friday. More than 70 percent of Americans now live in states where same-sex marriage is legal.

Federal judges in all four states under the 6th Circuit Court of Appeals — Kentucky, Michigan, Ohio and Tennessee — also struck down marriage bans in those states. However, in November a three-judge panel of the 6th Circuit upheld the states’ right to bar same-sex marriage, creating a schism between interpretations of Windsor and making Supreme Court mediation inevitable.

It’s not a surprise to many that the DeBoer case was among those the Supreme Court accepted, in part because it has the most complete record. It is the only case among those considered post-Windsor in which a federal district court judge held a trial with expert testimony and cross-examination. In every other case, federal district judges have ruled on the basis of oral arguments and court filings.

Kennedy is viewed as the swing justice, with four justices each believed to side for and against same-sex marriage. In addition to the Windsor decision, Kennedy wrote a 1996 opinion prohibiting Colorado from barring local laws that protect gays and lesbians from discrimination and the 2003 decision Lawrence v. Texas, which struck down laws punishing adult consensual sexual conduct between people of the same sex.

Still, it remains unclear how Kennedy will rule on the direct question of a constitutional right to same-sex marriage. Court watchers were surprised in October when the justices did not take up the gay marriage issue because a minimum of four justices is needed to take on a case, and neither side chose to do so. At the time, however, there was no disagreement among the circuits; that happened only when the 6th Circuit ruled in November.

“It is very curious that they didn’t get four votes to take this up until now,” said Robin Fretwell Wilson, a professor at the University of Illinois College of Law. “If it was that much of a no-brainer how Kennedy will go, one side or the other would have done it before this.”

Many believe the Supreme Court’s reluctance to move faster on the marriage question has been an effort to give the nation a chance to adjust to the idea. Opinion polls have shown a stunning change in public support, which has surged to 59 percent nationwide, according to a March 2014 Washington Post/ABC News poll. In 2005, the same poll found just 37 percent support.

Opponents of same-sex marriage warn that a court decision forcing it on states could polarize the nation, as Roe v. Wade, the 1973 ruling that women have a constitutional right to have abortions, has done.

“It can be a landmark of Dred Scott proportions, Roe v. Wade proportions and Plessy v. Ferguson proportions if the Supreme Court tries to constitutionalize a right that’s not in the Constitution, and then the American public will have to react to that and be deeply divided,” said John Eastman, chairman of the National Organization for Marriage, which believes same-sex marriage damages children and discourages straight people from getting married. “Or it can be a constitutional landmark that supports the policy of letting the people decide for themselves how to proceed with controversial topics rather than the Supreme Court.”

Dred Scott is the 1857 decision that reinforced the legality of slavery, outraging abolitionists and pushing the country toward the Civil War. Plessy is the 1896 case that upheld racial segregation.

Indiana University law professor Steve Sanders dismissed Eastman’s comments as “puerile, over-the-top” rhetoric, saying, “Dred Scott and Plessy are widely known to be constitutional abominations that were hateful and oppressed people.”

Wilson said it’s unlikely the Supreme Court would reverse so many circuit court decisions and trigger the chaos that could occur in states where gay marriage has been legalized. Yet Kennedy may feel the need to include language in his opinion that reassures conservatives and religious people who object to homosexuality.

“I just think it would be wise for the court to leave a space for legislators to carve out religious exceptions,” she said. “The whole challenge here is to not have a Roe moment, to not have a decision on same-sex marriage that creates the kind of divides that we still have 40 years later with abortion.”