[brightball]

It is the 10th amendment, part of the Bill of Rights.

"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."

I'm aware of the Supreme Court interpretation of it but there are also a number of people who contest that particular interpretation, as people do on multiple Supreme Court rulings.

Totally agree with you on the highway funding thing. That's basically the tax equivalent of taking your wallet and then telling you what you have to do to get it back. It was one of the earliest recent examples of a Federal power grab and if I'm not mistake that was actually Reagan.