In the Parker v. Illinois case of 1947, the U.S Supreme Court ruled that a state could regulate interstate commerce if it was necessary to protect public health and safety. The case involved an Illinois law requiring all milk sold in the state to be pasteurized, which affected out-of-state dairy farmers who wanted to sell raw milk in Illinois. The plaintiffs argued that this law violated their rights under the Commerce Clause of the Constitution by interfering with interstate commerce. However, the court upheld the law on grounds of protecting public health and safety from potential diseases associated with consuming raw milk. This ruling affirmed states' police powers over matters within their borders even when they affect interstate trade.

In the dissenting opinion for Parker v. Illinois, Justice Frank Murphy argued that the majority's decision failed to adequately protect an individual's constitutional right to a fair trial. He contended that the defendant was not given sufficient time or resources to prepare his defense and was therefore denied due process of law under the Fourteenth Amendment. Furthermore, he disagreed with the majority’s view on waiver of counsel, asserting that it should be clearly established whether a defendant has knowingly and intelligently waived their right to legal representation before proceeding without counsel in court proceedings. The lack of clarity surrounding this issue in Mr. Parker’s case led him to believe there had been a miscarriage of justice which undermined faith in America’s judicial system as one committed to ensuring fairness and equality before law.