Replying to 20 inch blades on the impala

REALLY need some outside perspective on this situation:

My brother's in high school and I'm away in college. My brother just started smoking weed heavily / dealing in my hometown. It's starting to get really confrontational between my mom and him ever since she found out. He looks up to me ALOT but knows I smoke at college a decent amount. Only difference is it's not affecting my life in negative ways like its starting to affect his (i.e. getting a bad rap at school, teachers definitely have caught on, etc.) It's pretty much his ATTITUDE thats the problem, not the weed smoking necessarily. Towards my mom its a: "Yea I'm doing it, the fuck are you going to do to stop me?" attitude. Towards me its a : "Theres nothing else to do in this boring ass town" attitude.

My question:
I don't mind if he smokes and it doesn't negatively impact him / his future, but how do I tell / show him to stop fucking around?

I pretty much feel like I have the perfect opportunity to pull him out of this while he's in shallow waters.

Any input would be appreciated.