NightTrain
Veteran XX
I seem to remember a few cases from civics class. Something about making the legal age to drink 21 or something. If states didn't comply (they didn't have too), but they would not receive federal funding for roads.
This could be complete bs, I'm trying to pull a memory out of my ass from 20 years ago.
Edit: Holy shit I actually learned something in High School.
It was also used to create 55mph speed limits and helmet laws.