do i have a right to proof that he's keeping clean?

ok so my boyfriend has a weed addiction and since he got caught steeling some money from someone he's been getting himself better and not smoking (or so he says). if he's prepared to get himself better then i'm prepared to give him a chance (i love him and want the best for him and want to be with him).

now i was nosy in his box where he keeps his stuff and he had a grinder in there which he wouldn't need if he was clean. also yesterday whilst i was visiting him he borrowed my phone to make a call then deleted my call history so i wouldn't see the number (not that i'd do anything with it anyway). that to me was suspicious in my books.

i've kinda guessed he's still doing some but a) don't want to believe it and b) haven't said anything cos we dont really talk about it and when we do he doesn't say much.

do i have a right to see in his box or for him to prove to me that he's clean. if he is then whatever i ask to see he won't have a problem with it. i know he can get clean and get a better life for himself and i dont want to see him back when he was at his lowest and selling things etc.

what would you do if you we're me and how would you talk to him about it