Feds approve Cadillac CT6 digital rearview mirror
Because it still functions as a standard mirror, NHTSA had no problem approving it for use in the US.

We don't often get the latest and greatest in-car tech in the US, and we have some outdated laws to thank for that -- it's why we likely won't receive laser headlights for some time. But not every cool bauble is banned from our roadways. In fact, the feds just approved a trick piece of hardware in the forthcoming Cadillac CT6.
The CT6's rearview mirror functions like any other -- until you flip a switch. Then, it turns into a screen, displaying a live feed from the backup camera. The goal is to enhance visibility and reduce blind spots with a wider field of view -- it also works when, say, you've loaded the rear seat up to the ceiling, or if you have some particularly tall passengers.
There was concern that the new mirror didn't meet federal safety standards, but the National Highway Traffic Safety Administration (NHTSA) put that to rest by approving the mirror, citing its retained functionality as a traditional mirror. Basically, just because the mirror also does something else doesn't preclude it from acting in a traditional manner.
This is good news for General Motors, as the automaker had planned to install this mirror in two other forthcoming vehicles -- the Cadillac XT5 crossover and the Chevrolet Bolt EV. Nissan also briefly toyed with this technology, but it has yet to arrive on a production model.