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 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.