NHTSA also pointed to its rules for advertising of crash-test results, which discourage the use of "potentially misleading words such as 'perfect,' 'safest,' 'flawless' or 'best in class' to describe the star rating received by the vehicle."
To think that Tesla could have been even bolder. The company's founder and CEO, Elon Musk, said during a July interview with Bloomberg that the Model S would get "six- or seven-star ratings" if the government's ratings went that high.
Tesla probably won't face any serious consequences for its claims, but the company may someday regret its reluctance to play nice with regulators.
For better or for worse, there is a good reason most car companies don't pick fights with the people who write the rules.