Lawyers at Gibson, Dunn & Crutcher for Uber and Postmates are due in court on Friday to ask a federal judge to halt enforcement of a California employment law that, according to them, would raise the ride-sharing firm’s costs and harm its drivers and customers.

The law, Assembly Bill 5, which went into effect on Jan. 1, mandates that certain individuals considered independent contractors in California will now be employees. The idea was to remedy what many considered the widespread exploitation of California’s workers, but Uber Technologies Inc., Postmates Inc. and two of their drivers sued on Dec. 30, invoking the Constitution to stop enforcement of the law.