Yesterday, Uber announced that it is now offering rides in self-driving vehicles for users in San Francisco — an announcement that apparently came as a surprise to the California Department of Motor Vehicles, which has advised the ridesharing service that it is breaking the law by operating this autonomous cars without DMV approval.

In a letter [PDF] sent Wednesday afternoon by the DMV’s Chief Counsel to Uber’s Anthony Levandowski, the agency points out that the California Vehicle Code only allows for testing of autonomous cars in real-world settings if the operator of these vehicles has applied for and received a permit to do such testing.

“Had Uber obtained an autonomous vehicle testing permit prior to today, the company’s launch would have been permissible,” writes the DMV. “However, it is illegal for the company to operate its self-driving vehicles on public roads until it receives an autonomous vehicle testing permit.”

The DMV has directed Uber to cease operations of these self-driving cars until it has complied with state regulations.

“If Uber does not confirm immediately that it will stop its launch and seek a testing permit, DMV will initiate legal action, including, but not limited to, seeking injunctive relief.”

While the Uber vehicles are self-driving, the company has maintained that they are not operating with full autonomy. In San Francisco and Pittsburgh — the two cities where Uber now has these tricked out Volvo vehicles — there are two people in the front seats: a person who is supposed to keep their hands lightly on the wheel at all times and be ready to intervene, and a tech taking notes.

However, the DMV tells the Wall Street Journal that just because someone is sitting behind the steering wheel doesn’t mean the car can avoid the requirement for a self-driving permit.

“They’ve equipped the vehicles with technology that allows them to operate autonomously and that’s the key,” says the DMV’s Chief Counsel.

We’ve reached out to Uber for comment and will update if we hear back from the company.

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