I thought this was interesting, perhaps you will to
essentially the argument was that 18 was too young (based supposedly on stats, although it appears to be mostly gut instinct) due to single vehicle late night accidents; and that if a neighbouring state had a lower drinking age you young folk (GET OF MY LAWN WITH YOUR 3.2 BEER!) would dangerously drive to that state, then return inebriated even more dangerously
so the pres. withholds highway funding to states until they bend to his will to raise the drinking age; which the supreme court upholds when a state contests it.
and that is why you can go to war for the US, but not down a beer to steel your nerves before doing so