SAN FRANCISCO — In a challenge to state authority, Uber is refusing to seek a permit for the self-driving cars it rolled out in San Francisco on Wednesday, prompting California regulators to immediately attempt to shut down the program.

The Department of Motor Vehicles, which regulates the use of autonomous vehicles on the state’s roadways, demanded that Uber obtain the proper permit or face legal action. Until Uber complies, regulators wrote Wednesday in a letter to Uber, the company must stop testing its cars on public streets.

“These requirements serve to build public trust in the safety of the technology and to foster confidence in allowing autonomous vehicles on public streets,” DMV deputy director and chief counsel Brian Soublet wrote in the letter. “Had Uber obtained an autonomous vehicle testing permit prior to today, the company’s launch would have been permissible. However, it is illegal for the company to operate its self-driving vehicles on public roads until it receives on autonomous vehicle testing permit.”

But instead of backing down, Uber is taking a hard-line stance against what it deems to be excessive regulation, seemingly hoping to change the rules with its act of defiance.

“There is a more fundamental point — how and when companies should be able to engineer and operate self-driving technology,” Anthony Levandowski, head of Uber’s Advanced Technology Group, wrote in a blog post Wednesday.

“We have seen different approaches to this question. Most states see the potential benefits, especially when it comes to road safety. And several cities and states have recognized that complex rules and requirements could have the unintended consequence of slowing innovation … Our hope is that California, our home state and a leader in much of the world’s dynamism, will take a similar view,” the blog continued.

The DMV released a public statement Tuesday night warning Uber that it is not exempt from state regulation.

“We have a permitting process in place to ensure public safety as this technology is being tested,” a DMV representative wrote. “Twenty manufacturers have already obtained permits to test hundreds of cars on California roads. Uber shall do the same.”

But California defines “autonomous vehicles” as vehicles that can drive without a human operator. Uber says its cars don’t count because they always have a driver behind the wheel ready to take control if the car encounters a situation it can’t navigate. Uber intends to launch driverless cars in the future, but the technology isn’t there yet.

Uber’s argument takes the DMV’s rules literally, but goes against the spirit of the regulations, said Bryant Walker Smith, a law professor at the University of South Carolina and scholar with Stanford Law School who specializes in autonomous driving.

“You can make this argument, but it’s not one that’s going to make you friends,” he said.

Uber’s stance is especially troublesome because California doesn’t allow any self-driving cars on public roads without someone in the car to take over if needed.  Google, for example, has drivers on board when it tests its autonomous cars. If the state adopted Uber’s logic, no self-driving car companies would need a permit, Smith said.

To be permitted to test autonomous vehicles, companies must pay an annual $150 fee (or more if they want to test more than 10 cars), obtain $5 million in insurance coverage and submit regular reports detailing accidents and instances where the car’s human operator had to take control of the vehicle.

“Uber has not provided a single example of how those regulations would prevent it from testing vehicles as they are proposing,” a DMV representative wrote in an email to this newspaper.

California’s self-driving vehicle rules don’t include penalties for companies that refuse to apply for permits, meaning the DMV may have to get creative if it wants to crack down on Uber.

The DMV could clarify its regulations, Smith said, and specify that self-driving cars require a permit whether or not there is a human driver behind the wheel. Or the department could say a self-driving car operating without a permit is unsafe, and move to revoke the vehicle’s registration. The California Highway Patrol could even issue tickets to self-driving Ubers.

On Wednesday political action group Consumer Watchdog called for San Francisco police to impound Uber’s “renegade robot cars,” and for the city attorney to file criminal charges against CEO Travis Kalanick.

“Uber is essential driving without a license and its CEO Kalanick should be treated like anyone else who does that,” John Simpson, Consumer Watchdog’s privacy project director, wrote in a news release.

Reports already have surfaced of self-driving Ubers disobeying traffic rules. A video posted on YouTube appears to show one of the cars blowing through a red light in front of the San Francisco Museum of Modern Art, as a pedestrian starts to cross the street. Charles Rotter, operations manager at Luxor Cab, said the video was shot Wednesday morning from a dashboard camera in one of the company’s taxis.

Uber says the car in the video was not part of its self-driving pilot.

“This incident was due to human error,” a company representative wrote in an emailed statement. “This is why we believe so much in making the roads safer by building self-driving Ubers. This vehicle was not part of the pilot and was not carrying customers. The driver involved has been suspended while we continue to investigate.”

Uber has a long track record of rocking the regulatory boat. The company’s innovative ride-hailing business model caused an uproar when it started because Uber evaded the rules that apply to traditional taxis. Instead of acquiescing to those rules, Uber worked with regulators to create new rules for ride-hailing services. The company also has fought back against regulators in Austin who tried to force drivers to undergo fingerprint background checks, and has resisted demands to give its drivers employee status.

Marisa Kendall is a technology reporter for The Mercury News, where she covers venture capital and startups. She has previously written about Silicon Valley court cases for The Recorder, and served as a crime reporter for The News-Press in Southwest Florida.