A Nebraska law prohibited any "partial birth abortion" unless that procedure was necessary to save the mother's life. It defined "partial birth abortion" as a procedure in which the doctor "partially delivers vaginally a living unborn child before killing the... child," and defined the latter phrase to mean "intentionally delivering into the vagina a living unborn child, or a substantial portion thereof, for the purpose of performing a procedure that the [abortionist] knows will kill the... child and does kill the... child." Violation of the law is a felony, and it provides for the automatic revocation of a convicted doctor's state license to practice medicine. Leroy Carhart, a Nebraska physician who performs abortions in a clinical setting, brought suit seeking a declaration that the statute violates the U.S. Constitution, claiming the law was unconstitutionally vague and placed an undue burden on himself and female patients seeking abortions. The District Court held the statute unconstitutional. The Court of Appeals affirmed.
https://www.oyez.org/cases/1999/99-830