Supporters of same-sex marriage argue that prohibiting gay and lesbian couples from marrying is inherently discriminatory and therefore violates the US Constitution’s 14th Amendment. But there are actually two ways to look at how same-sex marriage bans may violate the 14th Amendment.
The first and most popular argument cites the 14th Amendment’s Equal Protection Clause, which says states must guarantee equal protection under all laws to all groups of people. Same-sex marriage advocates argue this means states can’t exclude gay and lesbian couples from their marriage laws.
The second argument cites the 14th Amendment’s Due Process Clause, which says that no group should be unlawfully denied a fundamental right. Marriage equality proponents argue this should prevent states from denying gay and lesbian couples the right to marry, which has been recognized by the Supreme Court in the past.
In 1967, the Supreme Court applied both of these standards in Loving v. Virginia when the court decided that the 14th Amendment prohibits states from banning interracial couples from marrying.
”This case presents a constitutional question never addressed by this Court: whether a statutory scheme adopted by the State of Virginia to prevent marriages between persons solely on the basis of racial classifications violates the Equal Protection and Due Process Clauses of the Fourteenth Amendment,” Chief Justice Earl Warren wrote in the majority opinion at the time. “For reasons which seem to us to reflect the central meaning of those constitutional commands, we conclude that these statutes cannot stand consistently with the Fourteenth Amendment.”
A majority of justices at the Supreme Court concluded that very similar arguments applied to states’ same-sex marriage bans, meaning that marriage is a fundamental right, the bans were discriminatory and unconstitutional, and states must carry out and recognize same-sex marriages.