From the NY Times:
WASHINGTON — The Supreme Court on Tuesday will hear arguments on whether there is a constitutional right to same-sex marriage. The session, scheduled to last two and a half hours, is the last public step before a decision, expected in June, that will resolve one of the great open questions in modern constitutional law.
Until recently, the court has been cautious and halting in addressing same-sex marriage, signaling that it did not want to outpace public support and developments in the states. Now, though, a definitive decision will probably be handed down in about two months.
In 2013, the justices ducked the question that they will now consider. At the time, however, just 12 states and the District of Columbia allowed gay and lesbian couples to marry. Similarly, the court in October refused to hear appeals from rulings allowing same-sex marriage in five states.
That decision immediately expanded the number of states with same-sex marriage to 24, up from 19. The number has since grown to at least 36, and more than 70 percent of the nation lives in states that allow same-sex marriage.