More than 100 protesters were marching northbound on the bridge's pedestrian walkway when the California Highway Patrol stopped them and forced them to turn around.
A CHP spokesman said the protesters had a permit to gather on the bridge only until 2 p.m. When protesters did not leave by that time, officers forced them to return to San Francisco.
The protest was organized by the All People's Coalition to Stop U.S. Terror and Occupation.
In an unrelated case, a man jumped to his death off the Golden Gate Bridge just before the protest started, the Marin County Coroner's Office reported.
Coroner's investigators are asking for help in identifying the man, who died on impact after jumping from the middle of the bridge at around 12:35 p.m. There was no identification on his body and no fingerprint match.
He is a balding white man between 55 and 65 years old, 6 feet, 250 pounds, with graying brown hair and blue eyes. He was wearing bluejeans, a beige and green paisley polo shirt, and a black jacket with a Chevrolet insignia and the motto ``Heartbeat of America.''
Anyone with information is asked to call the Marin County Sheriff's Office at (415) 499-7234.