Here is a long, 99-page article (pdf) by Bryant Walker Smith suggesting the answer might be “yes.”
My argument is less subtle than those in the footnotes of the paper. Try running a driverless car in Fairfax City, or Alabama for that matter, while sleeping in the back seat with your feet up. See what happens when you drive by an alert policeman. (By the way, if you are asleep will your driverless car respond to the police siren and pull over?)
Let’s say you sit at the wheel while the software drives, you still are pulled over, and given a ticket for “reckless driving.” You show up in court and the judge asks you what regulatory inspection or safety process your equipment has been through. I am not saying you will always lose the case or indeed always will be pulled over, but your vehicle is no longer a reliable source of hassle-free transportation, no matter what statutory arguments you may make on your behalf.
There are different notions of the word “legal,” but from a practical point of view what the police will let you get away with is surely relevant. It seems to me that your protected sphere here is quite small.
For the pointer I thank Jerry Brito.