Can public school officials, acting under state authority, forbid girls from wearing pants? Bonnie Peltier didn’t think so.

In 2015 Peltier, the mother of a Leland, North Carolina kindergartener, complained about a rule at her daughter’s charter school compelling girls to wear skirts or dresses. Baker Mitchell, owner of the private, for-profit company that manages the school, responded by explaining that the policy was designed to preserve “chivalry” — which he later characterized as a code of conduct wherein women are “regarded as a fragile vessel that men are supposed to take care of.”

The following year, three future “fragile vessels” — Peltier’s daughter, a fourth grader, and an eighth grader — became plaintiffs in an ACLU lawsuit alleging that Charter Day School (CDS) had violated the US Constitution by imposing a rule that made it harder for girls to stay warm, feel comfortable, and play freely. An extensive legal battle followed, with a federal court ultimately deciding that CDS had indeed run afoul of the Fourteenth Amendment, which prohibits gender-based discrimination, by making the girls wear skirts.