The justices will consider four cases from Michigan, Ohio, Kentucky and Tennessee, consolidated and heard together. They will hear 2 1/2 hours of oral arguments in April and issue a ruling before the current term ends in late June.
The new challenge to states' gay marriage bans is destined to become even more of a landmark than the two cases decided by the court in 2013 — United States v. Windsor, which forced the federal government to recognize gay marriages, and Hollingsworth v. Perry, which made California the 13th state to allow them.
Those rulings, while historic, did not resolve the threshold questions in the debate: whether gays and lesbians have a constitutional right to marry, or whether states have the right to ban the practice. This spring's case will answer those questions.
"This is the beginning of the end game on the freedom to marry," said James Esseks, who leads the effort for the American Civil Liberties Union.
