The Carpenter v. United States case in 1987 revolved around the issue of insider trading and whether confidential information constitutes property under the mail and wire fraud statutes. The Supreme Court ruled that a Wall Street Journal reporter's tips to stockbrokers about upcoming articles constituted fraud, as they were not public knowledge yet. The court held that confidential business information is indeed a form of property, protected by these laws against unauthorized use or disclosure for personal benefit. This ruling expanded the definition of property rights to include intangible assets such as proprietary information, thereby broadening the scope of what could be considered fraudulent activity under federal law.

In the dissenting opinion for Carpenter et al. v. United States, Justice Blackmun argued that the majority's decision was a significant departure from established Fourth Amendment jurisprudence and could have far-reaching implications for privacy rights in America. He contended that by ruling that individuals do not have a reasonable expectation of privacy in their public movements, as tracked through third-party records like those kept by phone companies, the Court had effectively given law enforcement agencies unrestricted access to detailed personal information without requiring them to obtain a warrant or demonstrate probable cause. This, he believed, would undermine citizens' ability to go about their daily lives free from unwarranted government surveillance and intrusion. Furthermore, Justice Blackmun criticized the majority's reliance on outdated precedents which did not take into account modern technological advancements and societal norms regarding privacy expectations.