A group of Uber and Lyft drivers in California filed a lawsuit Tuesday in state supreme court to overturn a ballot measure that allows the companies to continue treating its workers like independent contractors.

The drivers claim that Prop 22, which was approved by California voters last November, violates the state’s constitution by “stripping” the state legislature’s ability to empower workers to organize, as well as by “illegally” excluding ride-hail drivers from the state workers’ compensation program.

“Every day, rideshare drivers like me struggle to make ends meet because companies like Uber and Lyft prioritize corporate profits over our wellbeing,” plaintiff Saori Okawa said in a statement. “With Prop 22, they’re not just ignoring our health and safety — they’re discarding our state’s constitution.”

The drivers challenging the constitutionality of Prop 22 are being supported by labor unions like SEIU and the California Labor Federation, which unsuccessfully opposed the measure in the run-up to the election.

But ultimately labor was outspent and outmaneuvered by companies like Uber, Lyft, and DoorDash, which poured over $200 million into the “Yes on 22” campaign to exempt them from a California state law that would require them to treat their workers like employees. The companies aggressively opposed the law, arguing it would eliminate driver flexibility, while also increasing consumer prices and wait times.

The law, AB5, represented an existential crisis for the companies, none of which have ever turned a profit and which have pursued costly efforts to develop autonomous technology in the hopes of eventually replacing drivers and delivery workers entirely. In response, the companies proposed a ballot measure that would keep their workers as contractors, while also providing a modicum of added benefits.

It’s unclear how successful drivers will be in overturning Prop 22. The measure was written in a way to withstand future challenges, including a provision that requires a seven-eighths majority of the state legislature for any modification, and ensuring that it will be all but impossible to invalidate.

But drivers are trying to use this language to argue that Prop 22 was illegal from its inception. The plaintiffs note that California’s state constitution gives the legislature “unlimited” authority to provide for a worker’s compensation system, “so that authority cannot be limited by a statutory initiative.”

“We look forward to the court affirming that gig companies cannot strip workers of their fundamental right to bargain for better pay and working conditions — and that corporations alone should not dictate the laws in our state,” said Bob Schoonover, president of SEIU Local 721 and SEIU California State Council, in a statement.

There have been ballot measures successfully repealed in California in the past, but mostly through additional ballot measures. If the lawsuit fails, drivers’ and supportive unions’ only other recourse to overturn Prop 22 may be another ballot initiative.

Drivers are organizing car caravans in San Francisco and Los Angeles in support of the lawsuit against Prop 22.