The Supreme Court of the United States (SCOTUS) held today by a vote of 5-4 that same sex couples have the same right to get married as opposite sex couples. Their right to do so is protected by the Equal Protection Clause of the Fourteenth Amendment to the United States Constitution. Justice Anthony Kennedy wrote the majority opinion joined by Breyer, Ginsburg, Sotomayor and Kagan. Roberts, Scalia, Thomas and Alito dissented.
On this same date in 2003, the SCOTUS struck down a Texas law criminalizing sex between two people belonging to the same sex and also on this same date in 2013, the SCOTUS dismissed an appeal over same-sex marriage on jurisdictional grounds clearing the way for same-sex marriages in California to resume.
The decision can be read here: PDF.