The city of Portland, Oregon, has sued Uber, ordering it to halt its service until it obtains the permits to operate legally.
"Uber and its drivers have failed to comply with the permit and other important public health and safety requirements," said a cease-and-desist order from the Portland Bureau of Transportation to Uber on Monday.
Neither Uber nor any of its contracted drivers has applied for or been granted driver or vehicle permits to operate within Portland as required by the Portland City Code, the lawsuit states.
Uber also has not obtained the minimum levels of insurance required to protect the public, the cease-and-desist order said.
An Uber spokeswoman, in an emailed statement, did not say how the company would respond to the order or lawsuit.
"Uber has received a tremendously warm welcome from riders and drivers in and around Portland," she said, referring to a petition with nearly 7,000 signatures. "Their support illustrates why it's time to modernize Portland transportation regulation."
"We remain hopeful that the city will listen to Portlanders who want safe, reliable, hassle-free ride options now," she said.
The city of Portland has already threatened to levy fines of US$1,000 to $5,000 against Uber drivers.
Portland's action is another in a series of moves by cities and regulators to block Uber's service on the grounds that it's illegal or otherwise not welcome. The company's launch in Las Vegas was stymied by a court ruling as soon as it began, and similar scenarios have played out in Austin, Texas, and Philadelphia.
Also on Monday, Uber was banned in Delhi after one of its drivers was charged with raping a female passenger.
It's unclear how Uber might alter its service in Portland following the lawsuit and cease-and-desist order. Uber already operates in Vancouver, Washington, less than 10 miles from Portland.