In the United States v. Simpson case of 1919, the Supreme Court dealt with issues related to mail fraud. The defendant, Simpson, was accused of using the U.S. Postal Service for fraudulent purposes by sending out deceptive letters and advertisements about a supposed "cure" for epilepsy that he sold through his company. He claimed that this product could completely cure epilepsy without any need for surgery or other medical intervention - a claim which was not supported by scientific evidence or accepted medical knowledge at the time. The court ruled against Simpson and upheld his conviction on charges of mail fraud under Section 215 of the Criminal Code (now codified as 18 U.S.C §1341). This decision reinforced legal precedents regarding false advertising and consumer protection in relation to postal services; it also underscored that making unfounded health claims about products can constitute criminal behavior if such claims are used to deceive consumers into purchasing said products.

The dissenting opinion in the United States v. Simpson case argued that the defendant's conviction for violating a federal law prohibiting interference with military recruitment during World War I should be overturned. The justice believed that Simpson, who was convicted for distributing anti-draft leaflets, was exercising his First Amendment rights to free speech and press. He contended that there was no clear evidence showing an immediate threat to public safety or national security due to Simpson’s actions; hence he did not believe it constituted "clear and present danger," which could justify limiting these constitutional protections. Furthermore, he expressed concern about the potential chilling effect on political discourse if such convictions were upheld as it would discourage citizens from expressing unpopular opinions out of fear of prosecution.