people are equal under law
Justice Anthony Kennedy, in Romer v. Evans (1996)
The Fourteenth Amendment's premise that no person shall be denied the equal protection of the law must coexist with the practical necessity that most legislation classifies [people] for one purpose or another, with resulting disadvantages to various groups or persons. . . . [The Court] has attempted to reconcile the principle with the reality by stating that, if a law neither burdens a fundamental right nor targets a suspect class [vulnerable group of citizens], we will uphold the legislative classification so long as it bears a rational relation to some legitimate end.
All laws rely on some form of classification, and in many instances the laws only apply to certain people and not to others, and people may be treated differently under terms of the same law. A pension plan for government workers, for example, could certainly differentiate the amount of the pension depending upon rank, years of service, and salary. Both criminal and civil law impose punishments that are clearly differentiated depending upon a number of circumstances. Two women, for example, who are both convicted of the same crime, say murder, could receive vastly different sentences depending upon the circumstances surrounding each case. Just as we would not want the law blatantly to discriminate against people on the basis of such characteristics as age, height, gender, race, or religion, at the same time, we would not want a law that forced all people, regardless of conditions, to be treated exactly alike.
The origins of the Fourteenth Amendment, as a blueprint for the reconstruction of the Confederate states after the Civil War, informed its interpretation in the courts for many years. Despite its plain language that does not in fact refer to race, everyone understood that the Congress that proposed the amendment meant to protect the former slaves from discrimination, and nothing else. Justice Harlan's famous comment that the Constitution was color-blind captured perfectly what had been intended.