The NHTSA doesn’t have as much regulatory authority as the FDA to enforce labeling standards. That’s the point I’m making. Their available mechanism is to go to court and sue Tesla for false advertisement. That may not be a priority for them, or they may not have the funding to do so. If Tesla were dealing with a different agency, one with explicit enforcement power, they’d be in a very different situation.
That’s not what Tesla is claiming. They are claiming that their 5 star vehicle is safer than all the other 5 star vehicles, and the NHTSA is saying that claim is not backed up by their test methodology.