The U.S. Supreme court has held, in a 5-4 decision, that all states must allow same sex marriages. Justice Anthony Kennedy wrote the majority opinion for the Court in the now landmark case of Obergefell v. Hodges. The case was argued on April 28, 2015 and decided today – June 26, 2015. The Court ruled that same sex couples have a constitutionally protected right to marry. The Court went on to state that the Fourteenth Amendment’s equal protection clause prohibits states from denying marriage licenses to those citizens. States are also now required to recognize the same-sex marriages of citizens in other states.
Chief Justice Roberts wrote a dissenting opinion and was joined by Justices Scalia and Thomas. Justice Scalia wrote a separate dissenting opinion joined by Justice Thomas. Justice Alito also wrote a dissenting opinion and was joined by Justices Scalia and Thomas.
To see the entire history and litany of opinions click on the link to the case: Obergefell v Hodges.