Comma.ai founder George Hotz, who has spent the good part of his past year criticizing competitors and their technologies, sent out a series of tweets Friday, saying that Comma.ai, a startup that aimed at offering semi-autonomous driving system, will be pulling out of the U.S. market in response to requests from federal regulators. From a Reuters report: The intervention, by the U.S. National Highway Traffic Safety Administration, came before Comma.ai began marketing its device. It is the latest signal that regulators want more control over the development and deployment of self-driving vehicle systems by vehicle manufacturers and suppliers, after a period in which they took a largely hands-off approach. The NHTSA on Friday disclosed an Oct. 27 letter to Comma.ai stating that the agency is investigating whether the company's device, called Comma One, complies with federal regulations. The letter and an accompanying special order demanded that Comma.ai provide the agency with information about the device and warned that the agency could prohibit the sale of the system if it were found to be defective.