OP just stahp would ya.

How about spending some time with your brother and find out what's really going on inside of his head?

Apparently he wants to isolate himself and stay stoned for some reason. Calling the police and turning him in is not gonna solve this problem, but instead complicate things. That move would affect you and your family.

Trust me, it could be a lot worse than smoking pot. If he was laying in there with dirty needles then you might have a real problem. Right now it sounds like he's depressed, and he's hiding from the world and trying to make things feel better. It's an escape. Maybe from you? Your parents? School? Why don't you get to know your brother and help lift them up. Think about it, it may come down to the point that one day you and he are all you have.