The United States Supreme Court has struck down a federal law that restricts the definition of marriage to opposite-sex couples and cleared the way for same-sex marriage in California.
The justices said that the Defense of Marriage Act discriminated against same-sex couples.
The ruling, on a 5-4 vote, means that legally married gay men and women are entitled to claim the same federal benefits that are available to opposite-sex married couples.
However, the court declined to rule on whether same-sex couples have a fundamental right to marry.
We have no authority to decide this case on the merits," Chief Justice John Roberts wrote in the opinion on a case brought against Proposition 8 in California.
The Defense of Marriage Act was signed into law in 1996 by former President Bill Clinton after it was approved in Congress. But it was subsequently struck down by several lower courts.
Twelve US states and the District of Columbia currently recognise gay marriage.