In a prior case involving a racially restrictive covenant, the Illinois Supreme Court determined that the covenant was valid and that because the action was a class action, all members of the class would be bound by the decision of the court. Hansberry (D), a black, purchased land from a party who had signed the same restrictive covenant forbidding the sale of the land to blacks. Lee (P), one of the parties to that covenant, sought to enforce the covenant based on the prior case involving the same covenant. D claimed that he and the party selling him the house were not bound by the res judicata effect of the prior decision because they were not parties to that litigation. D alleged a violation of their due process rights. The court held that the prior decision of the Illinois Supreme Court would have to be challenged directly in order to have it set aside or reversed. The court held that the prior action was binding on D. The case was appealed to the U.S. Supreme Court.