Mexico's Supreme Court has struck down language in a Jalisco state law that defines marriage as between a man and woman.
The decision means Jalisco becomes the fourth jurisdiction nationwide where gay couples can automatically get married, joining Coahuila and Quintana Roo states along with Mexico City.
Last year the Supreme Court issued a ruling saying it was unconstitutional for Mexican states to bar same-sex marriage.
But that decision was considered a "jurisprudential thesis" that did not invalidate state laws, meaning couples would have to sue for the right to marry and wait for the courts to rule in each individual case.
Tuesday's ruling establishes a generalized right for same-sex couples to wed in Jalisco, which is home to the country's second-largest city, Guadalajara.