Michael M. v. Superior Court of Sonoma County

Appeal of this decision was taken to the U.S. Supreme Court. The Court voted 5-4 to uphold the statute, but the majority could not agree on the reasons for doing so (this is called a plurality opinion). The Court stated that California's statutory rape law did not violate the Equal Protection Clause of the Fourteenth Amendment. Justice Rehnquist announced the Court's decision and Justices Brennan, White, Marshall and Stevens dissented.

Justice Rehnquist's opinion made many separate arguments in favor of the statute. First, the opinion stated that gender-based classifications were not "`inherently suspect' so as to be subject to so-called `strict scrutiny,' but will be upheld if they bear a `fair and substantial relationship' to legitimate state ends." In other words, the statute had only to prove some legitimate state end in order to be upheld. The purpose of the statute in preventing underage pregnancy was determined to be legitimate because of the potential harm that could be done to young women. They also expressed the opinion that pregnancy poses a health risk to young women, but does not pose such a risk to men.

What is more, the justices determined that the Equal Protection Clause of the Fourteenth Amendment does not necessarily require that any statute apply equally to everyone; nor does it require things which are different, such as the circumstances surrounding gender, to be treated the same. As long as the limitations or rules being selectively applied to one gender are based on realistic sex differences, the law can be seen as constitutional.

The opinion also considered whether the statute was necessary to deter teenage pregnancy. The defendants claimed that a gender neutral statute would serve equally well. Yet the justices claimed that this was not the question at issue; the statute may not have been drawn as precisely as it might have been, but the statute was within constitutional limitations. They also reasoned that a gender-neutral statute would reduce a woman's likelihood to report violations if she herself might be subject to prosecution. The concurring justices raised the possibility that a broad statute applicable to both sexes might, in fact, be unenforceable.

The argument also addressed the presumption that the scope of the statute might be too broad, since it makes it unlawful to have intercourse with young females who cannot become pregnant. Their opinion stated that the U.S. Constitution did not require the statute to limit its scope by excluding young girls; what is more, even if it did, the damage that very young girls can sustain from intercourse is reason enough to include them in the protection of the statute.

Finally, they determined that the statute was not unconstitutional because Michael M. was under 18 at the time of intercourse. The assumption by the state that the male is the aggressor and therefore culpable at the time was seen as legitimate. They held that the state prevented illegitimate pregnancy by providing men a deterrent for such aggressive action. The age of the man was seen as irrelevant, since both young men and old are capable of inflicting damage.