I find it amusing how the federal government was able to pass a national minimum drinking age – court precident at the time said the fed has no authority there – drinking limits have no interstate impact, so it’s purely down to each state to decide on it’s own. So a well-intentioned congressman decided to simply screw the intent of the constitution and work around it: A law was passed saying that any state which didn’t pass a law banning sale of alcohol to anyone under 21 would lose all it’s highway funding. Congress extorted the states into doing what it lacked the power to do for itsself.

I recall a very similar trick was used to extort states into passing the common religious exception to child-protection laws.

Since then, courts have expanded the power of the federal government considerably as a result of the War on Drugs – a lot of hard campaigning, legal trickery and sheer determination by anti-drugs campaigners concerned that states might decide to legalise various prohibited substances and so any such effort must be preempted by making sure the federal government has the ability to overrule them.