In 2008, the California Supreme Court held that prohibiting same-sex couples from getting married violated the state constitution’s equal protection clause. California voters passed a referendum known as “Proposition 8” that amended the state constitution to recognize a marriage only if between a man and a woman. The Supreme Court of California overruled a challenge to the amendment and held it was properly enacted. Two same-sex couples who wished to marry (plaintiffs) challenged the law in federal court against state and local officials, including the governor and attorney general (defendants). The officials refused to defend the suit, and the district court allowed the official proponents of the proposition (intervenors) to intervene and defend the law. The district court held the law unconstitutional and enjoined its enforcement. The officials did not appeal, but the intervenors appealed to the United States Court of Appeals for the Ninth Circuit, which certified a question to the California Supreme Court whether the intervenors had standing. The supreme court answered that the official proponents of the initiative were authorized under state law to defend the initiative, because the public officials had declined to do so. The Ninth Circuit thus concluded that the intervenors had standing to appeal under federal law. The Ninth Circuit affirmed the district court ruling on the merits, and the United States Supreme Court granted certiorari. The American Psychological Association and others filed an amicus brief on the merits, opining that homosexual parents are as likely as heterosexual parents to provide healthy environments for their children.