[1] Marcus clerked for United States District Judge John R. Bartels from 1971 until 1973, and joined the New York law firm of Botein, Hays, Sklar and Herzberg as an associate in 1974.
In 1980, Marcus was appointed the Chief of the Detroit Strike Force, Organized Crime and Racketeering Section of the United States Department of Justice.
[1] President Bill Clinton nominated Marcus to the United States Court of Appeals for the Eleventh Circuit, to a seat vacated by Judge Peter T. Fay, on September 25, 1997, after a previous Clinton nominee for the seat, Charles "Bud" Stack, had withdrawn his name from consideration after his background was raised as an issue by Bob Dole during the 1996 presidential election.
[5] In 2004, Marcus dissented when the court refused to rehear a case where the initial panel upheld a law banning LGBTQ couples from adopting children.
Marcus was joined by Gerald Bard Tjoflat and Charles R. Wilson, and Judges Barkett, Anderson, and Dubina filed separate dissents.
[7][8] In the 2021 case Burns v. Palm Beach, Marcus penned a lengthy dissent in which he argued that the First Amendment's protection of artistic expression extends to stylistic choices in residential architecture, subjecting aesthetic zoning measures to heightened constitutional scrutiny.