Let’s take a look at 4 scenarios...

There are 3 people in a family. Dad, mom and son John Doe. Here is a conversation between them:

Scenario 1

Mom : John now that you are out of high school, what do you plan on doing? College?
John : Actually I am thinking of joining the military.

(John is old enough to make a decision and enlist in the army)

Scenario 2

Dad : Hey John, you are 19 years old. Don’t you think its time you get an apartment or something?
John Doe : Yeah, I am looking.

(John is an adult and families have a conceived notion that once kids are over 18, they should move on with their own lives and get on their foot)

Scenario 3

John : Hey mom, dad. I have been seeing this girl for 4 years and I think I want to marry her.
Mom : You can’t marry now. You are only 19!
John Doe : I would hate to go against your wish but I am an adult and I have the right to marry if I want. Besides she is pregnant.

(John is an adult and yes he does have the right to marry and make that decision)

Scenario 4

Mom : John, I don’t appreciate you drinking before you are 21.
(Drunk) John Doe : Whatever mom. I am an adult and I am going to do whatever I want.

(John is a rebel and feels his adulthood is in stake by not having the opportunity to make his own decision on whether or not he should drink. Result : family tension, underground drinking, drinking problems. This leads to one problem after another and in worst case alcohol related death)

Well, that’s a great law! He is an adult enough to move out, marry against his parents will and yes enlist in the army. But he isn’t old enough to drink? You decide.