The California Supreme Court threw out a constitutional challenge to Proposition 22, clearing the path for the voter-approved law allowing gig companies to keep treating their workers as independent contractors.

The lawsuit that the state Supreme Court declined to hear was filed last month by a small group of app-based drivers and the Service Employees International Union, one of the nation’s largest labor unions. It alleges Proposition 22 limits the power of elected officials to govern, in violation of the California Constitution, by removing their ability to grant workers the right to organize and give access to the state workers’ compensation program.

The court’s decision Wednesday not to hear the case strengthens the position of gig economy companies, including Uber, Lyft and DoorDash, which spent hundreds of millions of dollars bankrolling the measure on the November ballot.