The contry can tell the states what to do and has many times.. one that I know about for this istance is the drinking age, set by states, but I think it was a mid west state.. one with no speed limits.. like s. dakota.. something.. didnt want to make the age 21 instead keep it at 18.. so what did uncle sam do??? didnt give them a penny for interstates and high ways.. what did s dakota do?? raised the age to 21.. and waalaa.. look at that.. a couple bucks for some stinking roads that under aged drinker's are goin to get killed on..