Equal protection clause
The equal protection clause is a part of the Fourteenth Amendment to the United States Constitution which provides that ?no state shall make or enforce any law which shall [...] deny to any person within its jurisdiction the equal protection of the laws.?
The amendment was enacted shortly after the American Civil War and the clause's primary goal was to ensure free and equal treatment for ex-slaves, especially in Confederate states (thus the emphasis on states and their laws). However, it was later interpreted as imposing a general restraint on the government's power to discriminate against people based on "classes" not only by race but also by sex, alienage, illegitimacy, wealth and any other class. Some classes are "protected classes" such as race, while laws regarding other classes are not subject to strict scrutiny. The equal protection clause was also interpreted as outlawing selective prosecution.
By its terms, the clause restrains only state governments. However, the Fifth Amendment's due process guarantee has been interpreted as imposing the same restrictions on the federal government.
An unresolved and important legal issue to the gay rights movement is the level of scrutiny the United States Supreme Court would apply to state and federal laws that prohibit same-sex unions.
Equal protection analysis
To determine whether a law violates the equal protection clause, the following analysis is done:
Does the law discriminate on the basis of race? (a "protected class") If so, apply "strict scrutiny": the law is unconstitutional unless it is the least restrictive means of serving a "compelling" government interest.
Does the law discriminate on the basis of sex? If so, apply "intermediate scrutiny": the law is unconstitutional unless it is "substantially related" to an "important" government interest. In past decisions "sex" has meant in regards to gender. If sex also means orientation, at least intermediate scrutiny could apply not only to gay rights cases such as same-sex marriage but also to polygamous and incestuous marriages.
Does the law discriminate on some other basis? If so, apply the "rational basis test": the law is unconstitutional unless it is "reasonably related" to a "legitimate" government interest.
