An ethical egoist could argue that a person should be able to use marijuana if they view it as being in their best interests to do so. Or, they might argue that since smoking marijuana is probably not in one's interests, that they shouldn't do it. Either way, they would support an individual's right to make that determination, and so would probably be opposed to a law outlawing marijuana use. One possible exception, or even a challenge, might be that an ethical egoist could view restricting other people's access to marijuana as being in their own best interests. But philosophically, ethical egoists believe that people should do what is best for themselves, and most believe in leaving others to do the same.