The legal fight started Wednesday morning when the ridesharing giant opened its fleet of autonomous Volvos to riders throughout the city. It did so without applying for a permit to test autonomous technology, arguing that California regulations governing the tech apply only to vehicles that don't require a human supervisor. There is always someone at the wheel of an autonomous Uber.

Within hours, California DMV counsel Brian Soublet told Levandowski in a letter that his agency would take legal action and seek an injunction if Uber did not immediately confirm that it would stop testing and seek a permit. Mayor Ed Lee called on Uber "to stop the unpermitted and unlawful testing of autonomous vehicles."

Uber's reply? Come at me, bros.