A standoff between Uber and the State of California became more serious on Friday when Uber rejected a demand to get permits for its self-driving car program and the state fired back with a threat of legal action.
The spat began earlier this week when Uber launched a fleet of self-driving cars in San Francisco. The company had not obtained autonomous driving permits for the cars, and California's Department of Motor Vehicles asked the company to stop the service until they were issued.
On Friday, Uber said no.
"We respectfully disagree with the California Department of Motor Vehicles legal interpretation of today’s autonomous regulations, in particular that Uber needs a testing permit to operate its self-driving cars in San Francisco," Anthony Levandowski, vice president of Uber's advanced technologies group, told reporters.
He said Uber believes the technology in its self-driving cars is akin to the autonomous mode in a Tesla. California law expressly excludes from the permit process cars with "collision avoidance or other similar systems."
Levandowski also said that self-driving Uber cars are not capable of operating without "active control or monitoring" of a human operator.
"It's hard to understand why the DMV would seek to require self-driving Ubers to get permits when it accepts that Tesla's autopilot technology does not need them," he said.
The state was not amused.
On Friday evening, DMV lawyers shot back, demanding Uber "immediately" remove its self-driving cars from state roadways until it has the required permits.
If the company doesn't comply, "the Attorney General will seek injunctive and other appropriate relief," California's Department of Justice wrote in a letter to Uber, which it shared via email.
What comes next is not clear.
Uber has stared down lawmakers before in California and elsewhere and defiantly continued to operate in the face of demands that it recognize local rules and regulations.