In what appears to be a showdown, Uber has defied California regulators’ order to pull its self-driving cars off the streets of San Francisco.

The tussle began last Wednesday when Uber began using 11 sensor-packed Volvo XC90 self-drivng SUVs in the city-by-the bay without permission.

Within hours, the state’s Department of Motor Vehicles (DMV) sent a letter to the ride-sharing company, saying that the service was illegal and the proper permits had not been granted to operate autonomous vehicles on public roads. In the letter, the DMV threatened legal action.

“If Uber does not confirm immediately that it will stop its launch and seek a testing permit, DMV will initiate legal action,” DMV Chief Counsel Brian Soublet wrote in the letter.

The two were expected to meet on Thursday to reach an agreement, which failed to happen, and on Friday it became clear that Uber was not going to back down.

“This rule just doesn’t apply to us,” Anthony Levandowski, who runs Uber’s autonomous car programs, said in a press call with reporters, USA Today reported.

“You don’t need to wear a belt and suspenders and whatever else if you’re wearing a dress,” he said.

Uber contends that under the letter of California law, the company does not need a permit because the motor vehicles department defines autonomous vehicles as those that drive “without the active physical control or monitoring of a natural person.”

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The company’s position is that the self-driving cars it is testing is no different from current advanced driver assistance systems like Tesla Motors’ Auto Pilot and other cars that help with parking and collision avoidance.

Uber says that when it tests the cars, it has people sitting in both the driver’s seat and the front passenger seat, both of whom monitor what the vehicle is doing and thinking.

The state responded again with a letter addressed to Levandowski from the DMV’s Soublet, stating that if Uber does not confirm immediately that it will stop its launch and seek a testing permit, the DMV will initiate legal action.

As least 20 other companieshave applied for and received the DMV permits to test on California roads, including Tesla, Ford, Google and Mercedes-Benz.

Uber isn’t picking a fight, said Levandowski, but is taking a stand.

The technology it employs is currently in use in the same vehicles it began testing in Pittsburg, PA last September and is already “commonplace on thousands of cars being driven today in the Bay area,” he said.

USA Today