California regulators have told Uber that it must stop its self-driving car service in San Francisco until it gets a state permit, according to a report from the Associated Press.

The service, which launched earlier today, is an expansion of a similar pilot program in Pittsburgh. However, California has a extensive regulatory structure around autonomous vehicles and requires companies testing the vehicles in the state to get permits from the California Department of Motor Vehicles.

The DMV sent a letter, obtained by The Verge, to Uber executive Anthony Levandowski stating that autonomous vehicles may only be tested on public roads if there is the appropriate permit in place and that “it is illegal” for Uber to operate its self-driving vehicles on public roads until it receives such a permit. The DMV says it will initiate legal action including, but not limited to, injunctive relief if Uber does not comply.

Uber does not have such a permit, claiming that California’s regulations don’t apply to its self-driving cars because they cannot be driven without a human monitoring the system from the driver’s seat. “All of our vehicles are compliant with applicable federal and state laws,” said an Uber spokesperson to The Verge.

The California DMV, it seems, disagrees. Multiple incidents of Uber cars running red lights in San Francisco were reported today as well, which will likely increase the regulatory scrutiny on Uber’s activities.

We have reached out to both the DMV and Uber for comment.