Romer v. Evans, 517 U.S. 620 (1996) held that a state Amendment, prohibiting the voters of Colorado from enacting any law, state or local, including homosexuals in the classes of persons protected by antidiscrimination laws, was unconstitutional under the Equal Protection clause of the Fourteenth Amendment.
The Amendment had been recommended to, and passed by the voters of Colorado with the argument that it prevented small enclaves of homosexuals in communities known for liberalism and/or depravity, such as Aspen, Colorado and Boulder, Colorado, from granting homosexuals "special privileges" that "normal", heterosexual people did not have. The result was Colorado Constitution, Art. II, § 30b, known as "Amendment 2", the designation given when it was submitted for referendum to the voters of Colorado. The amendment reads:
"No Protected Status Based on Homosexual, Lesbian, or Bisexual Orientation. Neither the State of Colorado, through any of its branches or departments, nor any of its agencies, political subdivisions, municipalities or school districts, shall enact, adopt or enforce any statute, regulation, ordinance or policy whereby homosexual, lesbian or bisexual orientation, conduct, practices or relationships shall constitute or otherwise be the basis of or entitle any person or class of persons to have or claim any minority status, quota preferences, protected status or claim of discrimination. This Section of the Constitution shall be in all respects self-executing."
Laws are much more likely to be declared unconstitutional under the Equal Protection Clause if the Court subjects the law to "strict scrutiny". "Strict scrutiny" applies if the law interferes with a fundamental right, or constitutes invidious discrimination against a suspect class.
In this case, one of these two routes to strict scrutiny was barred by precedent, Bowers v. Hardwick, 478 U.S. 186 (1986), which held that homosexuals were not a "suspect class", despite a history of invidious discrimination. The Court in Bowers further held that, historically, sodomy was a crime, not a fundamental right.
Lawyers challenging Amendment 2 noted that, while sodomy may not be a fundamental right, voting is, and Amendment 2 effectively barred homosexuals from engaging in self-serving political action. The Colorado judiciary found this argument persuasive, applied strict scrutiny, and the case made its way to the United States Supreme Court on a "fundamental rights" analysis.
The Supreme Court, however, found it unnecessary to go to the "strict" level of scrutiny. It applied the "rational basis test", used for reviewing laws which do not infringe on fundamental rights or disadvantage a suspect class. Usually, applying the "rational basis test" to a law means that it passes constitutional muster. If the government can come forward with any legitimate excuse or purpose for the law, the judiciary does not second-guess the political process which created the law, and allows it to stand.
Colorado first argued that the Amendment preserved the rights of landlords or employers who have personal or religious objections to homosexuality to freely discriminate against homosexuals. Discriminating against unpopular groups, however, is not a legitimate government objective. Colorado also argued it had an interest in conserving resources to fight discrimination against other groups. This argument would have been more persuasive if Amendment 2 had limited all antidiscrimination laws to groups which the Supreme Court has declared to be a "suspect class": race, religion, etc.. In fact, however, Colorado's state and local antidiscrimination law protected a variety of traits which the Supreme Court has not declared "suspect", but which appeal to conservative "pro-family" voters in Colorado (age, military status, marital status, pregnancy, parenthood, custody of a minor child, political affiliation, physical or mental disability). In the end, the Court held that Amendment 2 was so broad that the Court could not believe that "it was directed to any identifiable legitimate purpose or discrete objective" except, of course, the one not permitted by the Constitution: denying equal protection of the law to a particular group.
The Romer case was decided by a margin of 6-3 (Justices Kennedy, Stevens, O'Connor, Souter, Ginsberg and Breyer in the majority, leaving the three hard-core conservatives as dissenters: Rhenquist, Scalia and Thomas). The 1986 anti-gay precedent, Bowers v. Hardwick, was decided by a 5-4 vote of a different group of judges (Justices White, Burger, Powell, Rhenquist and O'Connor, with dissents from the liberals Blackmun, Brennan, Marshall and Stevens). Thus, even if Justice O'Connor sticks with her anti-sodomy vote in Bowers, there may be a 5-4 majority to overturn Bowers. And in fact, on December 2, 2002, the Court granted the writ of certiorari to review an anti-sodomy case, Lawrence v. Texas, No. 02-102.