Eisenstadt v. Baird (1972)
William Baird was convicted in Massachusetts of giving contraception to an unmarried woman in violation of a state law that said contraception could only be given by authorized distributors (which Baird was not) and then only to married couples.  The US Supreme Court ruled the law unconstitutional, stating there was no "rational basis" to distinguish between married and single people in this way, and that this was an "unwarranted governmental intrusion."

http://www.oyez.org/cases/1970-1979/1971/1971_70_17/