Answer
first try talking to your friend about your issues with this problem and second consider that marijuana doesn't cause a chemical addiction so s/he may just enjoy it and not be addicted, more info would be useful such as how much and how often does your friend smoke? also it wouldn't be a good idea to bring a government group into the picture on just marijuana because that would screw your friend over for going to college among other things. The best thing to do is talk to your friend in a way that isn't angry but expresses that you're concerned.