On post and ucmj if they leave post after drinking.
Should stay 21 anywhere else. But like someone said if they want it they will get it, that includes dope ect. Most 21 yo arn't mature enough to drink but it happens. I think that after you have say 3 drinking violations that it should be againts the law to drink alltogether!!
JUST MY 2 CENTS
And yes I am In the military 15YRS SFC (E7)
Very good stipulations. I like it.