President Barack Obama says today's Supreme Court ruling giving same-sex couples the right to marry nationwide represents a day when justice "arrives like a thunderbolt." Obama says the court's decision has "made our union a little more perfect."

Gay rights supporters cheered, danced and wept outside the court after the decision.

Justice Anthony Kennedy wrote the majority opinion, just as he did in the court's previous three major gay rights cases dating back to 1996. Today's ruling comes on the anniversary of two of those earlier decisions.

Chief Justice John Roberts dissented, saying the court "is not a legislature." Also dissenting were Justices Antonin Scalia, Samuel Alito and Clarence Thomas.

The 5-4 decision means that the 14 states that haven't allowed same-sex marriage will have to stop enforcing their bans.

The ruling won't necessarily take effect immediately, because the court gives the losing side roughly three weeks to ask for reconsideration.

But marriage licenses are already being issued in Georgia and some other states that banned same-sex marriage. In Atlanta, the Fulton County Probate Court clerk says three same-sex couples received marriage licenses this morning, and one of those couples has already married.

In Mississippi, Attorney General Jim Hood says gay marriages cannot take place immediately in state.