Sweet was married to Adele Hall Sweet, daughter of publisher Dorothy Schiff, who died at the age of 93 on December 21, 2018. He died on March 24, 2019, aged 96.
''Universal City Studios, Inc. v. Nintendo Co., Ltd.''
In 1982, Sweet ruled against Universal Studios, which sued Nintendo for alleged copyrightability between the character King Kong and the 1981 Nintendo video gameDonkey Kong. He stated that Universal didn't own the King Kong character since it was considered public domain, and knowingly brought the case in attempt to extract license agreements from companies incapable of or unwilling to confront Universal’s "profit center." Universal appealed the case in 1984, but the United States Court of Appeals for the Second Circuit sided with Sweet and reaffirmed his verdict. In 1985, Sweet ordered Universal to pay Nintendo $1.8 million for "legal fees, photocopying expenses, costs incurred creating graphs and charts, and lost revenues."
One controversial case he decided was Pelman v McDonald's Corp., a case involving a group of teenagers who sued McDonald's fast-food chain, claiming the food sold by McDonald's caused their obesity. Sweet accepted the case in 2003 and said "it is the place of the law to protect them against their own excesses". However, the plaintiffs appealed to United States Court of Appeals for the Second Circuit, and in 2005 the circuit court vacated the district court's dismissal and reinstated some of the claims as incorrectly dismissed.
In 2005, in New York Times v. Gonzales, Sweet decided that The New York Times can maintain the confidentiality of its sources, refusing to dismiss Times' suit against Department of Justice in the Judith Miller controversy. However, later the Second Circuit reversed his decision and allowed Special Prosecutor Patrick Fitzgerald to access phone records of New York Times journalists.
Sweet expressed strong opposition to the United States War on Drugs, saying the drug war is "expensive, ineffective and harmful" and that only "gangs and cartels benefit from current drug laws". In an interview with PBS, he said that the mandatory minimum sentence for drug offenses violates due process and separation of powers. With co-author Edward A. Harris he contributed a chapter to Jefferson Fish's book How to Legalize Drugs. Sweet was a member of Law Enforcement Against Prohibition, and served on its advisory board.
Gene patents
On March 29, 2010, in Association for Molecular Pathology, et al. v. United States Patent and Trademark Office, et al., Sweet ruled that Myriad Genetics' patent on BRCA1 and BRCA2, genes linked to breast cancer, were invalid for the reason that, in Sweet's opinion, genes do not constitute patentable subject matter. His decision was 156 pages long.