He has argued and written briefs that have been submitted to the United States Supreme Court; a number of which have resulted in changes in the law on a nationwide basis, including one described by Justice William J. Brennan as "probably the most important due process case in the Twentieth Century".
He has defended clients such as "Lenny Bruce, Samuel Beckett, Cesar Chavez, and Chuck D" and has "locked horns... with the Federal Government... and with writers and reporters," including Norman Mailer and Mike McAlary.
Though "a hero to liberals," Garbus drew controversy when "his dedication to the First Amendment led him to defend the right of Nazis to march through Skokie, Ill.," which "earned the enmity of many friends and colleagues.
"[8] In 2023 and 2024, several of Martin Garbus‘ high-profile, controversial cases have been featured in “All the Court’s a Stage,” a series of dramatic adaptations by Susan Charlotte, directed by Antony Marsellis and presented by Cause Célèbre Productions, a Not-for-Profit organization.
The series, based on the writings of Garbus, includes stories about the legal journeys of Samuel Beckett, Lenny Bruce, Daniel Ellsberg, Václav Havel, Henrietta Wright, Salman Rushdie, Andrei Sakharov, and "Jane Doe" and played to sold-out audiences in NY and LA.
In 2014, President Barack Obama traveled to Cuba with Mr. Garbus’ clients to facilitate an exchange that included the release of Gerardo Hernández and his brothers.
[citation needed] Mr. Garbus is a member of the Advisory Board, Center for Law, Brain & Behavior, Harvard Medical School Teaching Hospital and Massachusetts General Hospital After law school and after two years in the United States Army, he clerked for Emile Zola Berman, an internationally known trial lawyer who represented Sirhan Sirhan, and Ephraim London, a Supreme Court advocate and Constitutional lawyer whose firm represented Alger Hiss, and who won every one of the nine cases he argued before the Supreme Court.
He was director-counsel of the Roger Baldwin Foundation of the ACLU, which had offices in Florida, Mississippi, Atlanta, Georgia, Alabama, and California and now has a budget in excess of 2 hundred million dollars.
Some of the leading civil rights lawyers, for a period of time staffed these offices, including Charles Morgan, Armand Derfner, Al Bronstein, Bruce Ennis, and Richard Sobel.
[citation needed][10] Garbus was involved in the following notable cases: Other clients include Nelson Mandela, Andrei Sakharov, Václav Havel, Samuel Beckett, Al Pacino, Daniel Ellsberg, Philip Roth, Michael Moore, Sean Connery, Michael Caine, Michael York, Lauren Bacall, Agnes Martin, Pace Gallery, Estate of Mark Rothko, Robert Mapplethorpe, Cincinnati Museum of Fine Art, Robert Redford, Spike Lee, Sally Mann, Allen Ginsberg, Kathy Boudin, Garry Marshall, Marilyn Monroe, Igor Stravinsky, Nora Ephron, Salman Rushdie, Simon & Schuster, Random House, Bertelsmann, Penguin Books, Putnam,[13] Grove Press, The Sundance Film Festival, Alger Hiss, Ecuadorian plaintiffs, Estate of John Cheever, Julie Taymor, Justices in India, Knopf, Leonard Weinglass, Michael Bloomberg, Michael York, Mississippi Freedom Democratic Party, Philip Roth, Rwanda, Sean Connery, Sonny Mehta, Sophia Loren to clients, Steven Donziger, Susan Sontag, Viking Penguin, and William Kunstler.
He served as a commentator for NBC, ABC, CBS, PBS, Charlie Rose, CNN, Fox News, Court TV, CCTV in China and the BBC, Time and Newsweek.
[citation needed] Garbus' career is set forth in the award-winning HBO documentary Shouting Fire: Stories from the Edge of Free Speech.
He also spoke with Daniel Lelchuk, who runs the Talking Beats podcast, for a discussion of the first amendment—what it really means, and how perhaps, in this social media dominated era, there are implications that go far beyond what previously would have been just a person yelling in the town square that is reported by the local newspaper.