The Mark Cuban-backed event stages a quarter-mile course with up to 28 live bulls charging toward paying participants. Despite successfully staging eight American bull runs since August 2013, including one in Chicago earlier in July, animal rights activists have come together to try to shut down the event, suing its organizers.
A joint suit filed by the Animal Legal Defense Fund and PETA claims the Great Bull Run constitutes animal abuse and violates California's anti-cruelty and unfair competition law.
"It's an absurd spectacle that's totally unnecessary," ALDF attorney Matthew Liebman told NBC Bay Area.
"California prohibits forcing an animal to fight with either another animal or a human being, which is exactly what the Great Bull Run does ... At past events, our investigators have seen participants slap and punch the bulls as they run by. ... It's unnecessary to cause the animals to go through that stress for someone's temporary thrill."
Rob Dickens, CEO of the Great Bull Run, disagrees, calling the lawsuit "frivolous" and pointing out the double standard with rodeos and bull riding.
"They are claiming a lot of crazy things, including that we are abusing our bulls ... Rodeo bulls perform almost every weekend and have somebody strapped to their back kicking them with metal spurs -- that's not considered abuse, rodeos are legal in California."
PETA is openly opposed to rodeos, encouraging concerned citizens to "protest to local authorities, write letters to sponsors, leaflet at the gate, or hold a demonstration" if a rodeo is booked near their home.
Saturday's Great Bull Run will feature 18 live bulls.