The case of Michael M. v. Superior Court of Sonoma County in 1980 revolved around the constitutionality of a California law that criminalized sexual intercourse with a female under the age of 18, but not with a male under the same age. The defendant, Michael M., was charged with statutory rape after having sex with an underage girl and challenged this law as gender-biased and therefore unconstitutional under the Equal Protection Clause. However, in its ruling, the Supreme Court upheld California's statute by a vote of five to four on grounds that it served to prevent teenage pregnancies - an issue affecting only females - thus providing sufficient justification for differentiating between males and females in this context.

In the dissenting opinion of Michael M. v. Superior Court of Sonoma County, Justice William Rehnquist argued that the majority's decision to uphold California's statutory rape law was flawed because it did not adequately consider whether gender-based classifications were discriminatory under the Equal Protection Clause. He contended that while societal changes had reduced some differences between men and women, biological distinctions remained significant in certain contexts such as pregnancy and childbirth. Therefore, he believed laws could reflect these realities without being inherently sexist or unconstitutional. Furthermore, he criticized the majority for using a "realistic" approach rather than a strict scrutiny standard when evaluating this case - an approach which he felt allowed too much judicial discretion and undermined legal consistency.