I Have a Question About Drug Possession?

My brother is 16 and smokes weed, Ive told him not to bring any of that in my house because the neighborhood I live in is always checked by the police and Im concerned that they might try to come and search my house.If that happens and they find weed in my house what are the consequences? I know it depends the city I live in..I live in Los Angeles…I don;t know what to do anymore I always tell him that’s bad for him and even sent him to rehab ..stopped using it for a couple of months and the day he graduated his rehab that same day celebrated it by smoking the same thing so dont think I’m ok with him smoking it! Thanks!!