drinking alcohol at such a young age could impair brain development.
However on the other hand, something such as reporting escaped slaves is something completely different and not something that should be obeyed. I think the biggest difference with these two examples is the fact that an intoxicated teenager could potentially make a poor decision to get behind the wheel of a car and severely injure/kill someone . Whereas a slave that is trying to gain their freedom is not something that would harm anyone directly.
I think the notion of time also needs to be considered when discussing these two scenarios. Obviously being in the 21st century, it is hard for us to fathom turning someone into the state or national government because they are trying to gain their freedom because all of us have this notion/belief that America is a free country and we encourage people to live the "American Dream." However, things such as drinking laws or laws that prohibit certain types of drugs are obviously in place for a good reason.