Actually that law was passed under duress, if I am not mistaken, and might reasonably be considered invalid.
ML/NJ
Under duress as in the legislature and the Governor were physically threatened with violence, or under duress as in Federal Highway funds would be withheld if it were not passed?
Let's hear the reasonable argument that constitutionally protects 18-20 year old's right to purchase alcohol. Notice I didn't say right to 'drink.'
Likewise, an 18-20 year old's right to possess a long gun or handgun would not change, only their ability to purchase a long gun.
What if the 20 year old lived in New York City?