Yes, but states could, if they so cared, craft legislation that would protect existing dealers and allow for future innovation. Imagine a law that simply stated that a vehicle manufacturer has to declare up front whether a particular brand is going to be sold through dealers or directly from the manufacturer. There could be restrictions on changing that designation, like requiring they make the dealers "whole" (compensating for loss), or given them veto power to stop the change, etc. That would allow a new manufacturer, like Tesla, to enter the market, or an existing manufacturer to start up a new brand, like GM might have otherwise done with Saturn, via direct sales, without affecting dealers of existing brands.