I understand and agree with the reason behind the petition, but ultimately this is a state issue, not a federal one. So i wouldn't see this petition really doing anything meaningful. It's the whole basis of the 10 amendment.
The franchised dealership model is a failure, the dealerships cant do anything on their own initiative else they may lose the frnachise, and all they do is make it harder for the consumer to make an informed choice on a car purchase, and drives the cost up as well.
States COULD try to override the dealership laws (many states have laws that strengthen the Federal one), but thats like trying to herd cats.
I've read the FTC Commissioner's report on state laws here, and an economic analysis report that both cite state lawmakers as the responsible parties:
1. http://www.ftc.gov/speeches/leary/learystateautodealer.shtm
2. http://www.justice.gov/atr/public/eag/246374.htm
Arizona goes farther, apparently has a law that basically prevents manufacturers from releasing any information which might hurt the negotiating position of dealers. Needless to say, it's being challenged in court. Alliance of Auto Manufacturers v. Hull No. CIV 00-1324-PHX-PGR (D. Ariz. Apr. 30, 2001).
Look at the wording of the petition itself: "States should not be allowed to prevent Tesla Motors from selling cars directly to customer"
That doesn't sound like a federal issue to me.