The complaint hinges on a 2018 decision by the California Supreme Court establishing a new test for employment in the state. Under that decision, a company is required to classify workers as employees rather than contractors if it directs or controls their work; if the work they do is a usual part of the company’s business; or if the workers don’t typically operate an independent business performing the same work they perform for the company.

The measure the Legislature passed on Wednesday codifies and broadens that decision. Under the bill, anyone deemed to be an employee under the test would be entitled to protections like unemployment insurance, workers’ compensation and paid sick leave, not just a minimum wage and overtime pay.

In a call with reporters on Wednesday, Uber’s chief legal officer, Tony West, acknowledged the company faced a higher bar for demonstrating that drivers were truly independent contractors, but argued that “just because the test is hard doesn’t mean that we will not be able to pass it.” He alluded to “several previous rulings” finding that drivers perform a task that is “outside the usual course of Uber’s business” — suggesting the company could pass the second and potentially most challenging portion of the new test.

Neither Mr. West nor the company cited any specific court rulings to support this assertion. An Uber spokesman provided two examples of rulings from arbitrators rather than courts that had deemed drivers to be outside the company’s usual business.

Legal experts said Uber was unlikely to win on this claim in court. “Courts have not necessarily been receptive to that argument,” said Richard Meneghello, co-chairman of the gig-economy practice group at the law firm Fisher Phillips, which represents employers. “From a neutral perspective, it looks to be an uphill battle for the gig economy.”