First off, to all the people who say weed doesn't effect the body, it does. It is bad for you. Today weed is a lot stronger than it was 20 years ago, and has more unhealthy effects on the body. One joint has ten times the amount of tar than a cigarette((which besides nicotine is the worst partof a cigarette). Also if he thinks this is ok, he might move on to get a bigger high which would lead to him smoking more harmful substances. also smoking weed does permanent damage on the Frontal lobes. The decision process, emotional, and Behavioral part of the brain. It will deteriorate it, and you can imagine how that part of the brain is helpful? damage I am totally against smoking weed. Or anything for that matter. I would have a calm talk to him about what you found and that you disapprove. Tell him you won't ground him or do anything drastic if he promises not to do it anymore. If he does it anymore or any worse then you will take drastic measures. Tell him WHY you disapprove. Hope he chooses the right way to go for him. Everyone deserve the right to be happy, and depending on which path he wants to go down everything he does now effects it. Good luck, sorry for my grammar and spelling!