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The U.S. Supreme Court dismisses Baker v. Nelson, an appeal of a Minnesota Supreme Court ruling that found limiting marriage to opposite-sex couples did not violate the state constitution. The Court finds the case does not ask a substantial federal question, and some argue that dismissal set a binding precedent that could influence the Court's eventual consideration of Proposition 8.
1993
The Hawaii Supreme Court rules in Baehr v. Miike, finding that laws denying same-sex couples the right to marry violated state constitutional equal protection rights unless the state could show a "compelling reason" for such discrimination and sending the case back to trial court. The ruling was later credited with sparking a backlash in the form of laws and constitutional amendments defining marriage as the union of a man and a woman. Hawaiian voters later passed a referendum giving the legislature jurisdiction over marriage, bypassing state courts.
1996
Congress passes the Defense of Marriage Act, which is signed into law by President Bill Clinton. The law, popularly known as DOMA, allows states to refuse to recognize same-sex marriages and unions performed in other states. It also created a federal definition of marriage as between a man and a woman.
(And of course the list goes on...)