California has ordered Uber to stop trialling self-driving cars in the state, as it does not have necessary permits to do so.

Earlier this week, Uber announced that it would be bringing a small number of autonomous Volvo XC90 SUVs to its home town. Some of these vehicles will be assigned to pick up and drop off customers who request an UberX car.

In response, the state's Department of Motor Vehicles (DMV) sent a tersely worded letter to the controversial startup company.

The DMV noted that it had "developed regulations for manufacturer's testing of autonomous vehicles", that were "developed to foster technical innovation and ensure the safety of the motoring public".

According to the regulator, "twenty companies are approved to test a total of 130 test vehicles that are being driven by more than 480 permitted test drivers in California".

Uber has not done so, and if it "does not confirm immediately that it will stop its launch and seek a testing permit, DMV will initiate legal action".

On the day of the trial's launch, a self-driving Uber XC90 was filmed (above) by a taxi dashcam running a red light in the Marina District of San Francisco.

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An Uber spokeswoman told Automotive News"all of our vehicles are compliant with applicable federal and state laws".

In a post announcing the beginning of its San Francisco trial, the company stated bluntly that it didn't have any testing permits because "we don’t believe we [need to]".

Uber even hinted at possible public and legislative weariness about its 'do first, ask for permission later' philosophy, saying: "Before you think, 'there they go again' let us take a moment to explain..."

The ride-sharing firm argues that Californian regulations require a permit for "cars that can drive without someone controlling or monitoring them". Due to that fact that "it’s still early days and our cars are not yet ready to drive without a person monitoring them", Uber believes that it's exempt from requiring a permit.

It then goes on to criticise California for having "complex rules and requirements [that] could have the unintended consequence of slowing innovation", and hinting that other states and cities are more "pro technology".