It was probably a bribe. I mean the Feds offered so much in environmental cleanup funds that the states could hardly refuse.
But I would have to see the actual laws.
Actually I just went back and looked it up.
It falls under of all things Wickard vs. Filburn and the Commerce Clause.
“contribution to the demand for wheat may be trivial...his contribution taken together with that of many others similarly situated, is far from trivial.”
Environmental Law for Non-Lawyers, 1993 Ed. pg. 18