A unanimous ruling by the Mexican Supreme Court overturning a state law against same-sex marriage has opened the way for the eventual legalization of gay marriage across Mexico, legal experts say. The court ruled unconstitutional a law in southern Oaxaca state that defines marriage as a legal union between a man and a woman. The decision came in favor of three gay couples who sued Oaxaca state on grounds the law violated the principle of equal treatment for all citizens. Still, there won’t be any quick changes. Under Mexican law, two more cases from Oaxaca must be decided in the same way before a precedent is established allowing gay marriage — and only in that state. For each of Mexico’s 30 other states, five separate cases would have to be decided that way to establish precedent for gay marriage.