SAN FRANCISCO — A major labor union and several ride-hailing drivers are suing to overturn a newly passed ballot measure classifying gig workers as independent contractors in California.

The groups filed suit Tuesday in California’s Supreme Court, alleging Proposition 22 violates the state constitution and limits the power of state legislators to implement certain worker protections they are authorized to grant.

The suit, filed by Service Employees International Union and a group of ride-hailing drivers, asks the state Supreme Court to invalidate Prop 22, which cemented gig driver’s status as independent contractors after more than 58 percent of voters supported it in November. They argue the measure limits state legislators’ ability to implement a system of workers' compensation in defiance of their constitutional authority to do so. It also argues that the proposition unconstitutionally defines what comprises an amendment to the measure, as well as violating a rule limiting ballot measures to a single subject to prevent voter confusion.

The Protect App-Based Drivers and Services coalition, which represents gig companies such as Uber, Lyft and Doordash, criticized the lawsuit in a statement attributed to Uber driver Jim Pyatt, an activist who has worked in favor of Prop 22.

“Nearly 10 million California voters — including the vast majority of app-based drivers — passed Prop 22 to protect driver independence, while providing historic new protections," said Pyatt, of Modesto, who is retired and drives for Uber. "Voters across the political spectrum spoke loud and clear, passing Prop 22 in a landslide. Meritless lawsuits that seek to undermine the clear democratic will of the people do not stand up to scrutiny in the courts.”

It’s the latest turn in a heated saga that kicked off in 2019 when state legislators approved a law, known as Assembly Bill 5, that classified certain categories of gig workers as employees. Gig companies Uber and Lyft argued the law did not apply to them, but the courts sided with state and local officials, requiring the companies to classify drivers as employees. Meanwhile, the ride-hailing firms and food delivery giants such as DoorDash mounted a more than $200 million campaign, Prop 22, to fight the law. It aimed to provide limited benefits such as a wage promise and health insurance stipend in exchange for classifying drivers as independent, barring them from employee protections such as sick pay and workers’ compensation.

The groups that filed the suit, which also include SEIU California State Council, took particular issue with the measure’s inclusion of a provision requiring a seven-eighths legislative supermajority to amend and even define what constitutes an amendment. That authority, they say, is vested with the courts.

The lawsuit blasts the measure’s drafters as having “impermissibly usurped this Court’s authority to ‘say what the law is’ by determining what constitutes an ‘amendment.’” Further, they argued, they violated the single-subject rule by “burying these cryptic amendment provisions on subjects not substantively addressed in the measure, and in language that most voters would not understand."

They said they were suing in the state Supreme Court rather than a lower court because the issues were of broad public importance and required a speedy resolution to minimize harm to gig workers.