At 21 there's not much you can do about it legally.

When he's chewed his way through what savings he has, he'll either get a job (which should be a good thing) or he'll come home (also good).

I went through this with my middle child, and it's still not properly resolved 15 years later.

You can only trust that you have given him the tools to survive.

__________________
Calm, quiet, smooth, devastating