How do you imagine this working for someone who drives across Europe frequently, including sections of unrestricted Autobahn? Or someone who takes their street legal car onto (private) tracks from time to time?
Ideally, they'd just harmonize the speed limit in the EU; a majority in Germany approves of introducing a general speed limit on motorways anyways. But that'd hurt the bottom line of car manufacturers and we can't have that.
Also, GPS-validated speed limits for new cars. And I don't mean just the top speed in a country, I mean the posted speed limit on whatever road you are. Doesn't need to be a hard limit, in case of emergencies and for maneuvering, but make something interesting happen: online registration, enable the hazard lights, I'm sure there are many good options. It's ridiculous we're talking about fully automated driving and we don't even have this simple automation which would get rid of an entire class of everyday offense.
[1] https://de.wikipedia.org/wiki/Datei:Freeway_speed_limits_eur...
https://www.europarl.europa.eu/news/en/press-room/20190410IP...
It also wouldn't work on road sections with variable speed.
Variable speed roads, either make the limit the highest speed that's in the range, or come up with a way to communicate the current limit. Most new cars are always connected, anyways. And again, you can fail fast, at least initially. As with all driving aids, the person in the driver's seat bears the ultimate responsibility.
An example: A construction site goes away, raising the speed from 35 to 70mph. Someone governed to 35 is suddenly a virtually stationary obstacle. Theoretically (and legally), the onus is on the other drivers to avoid it, but practically speaking it's just begging for an accident.