the 10th amendment:
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
anyone looking towards federal intervention should consider this. the only way the feds could get involved if a case can be made that the state laws inhibit interstate commerce, and that would be a long battle
Exactly right. But the commerce clause issue is very relevant. This article in the Boston Globe is a must read: The fight for direct car sales - Opinion - The Boston Globe
Quote: But the thinking of many is that, if the court battles go onward and upward, the US Supreme Court will likely rule the entire auto franchise system unconstitutional; under the Interstate Commerce Clause, it would be seen as a restraint on trade. If so, the winners would not only be Tesla but all of us. Imagine how great it would be to buy your next car on Amazon — and even better, never have to deal with a car salesman again.