If they want to just make your joints disapear and not say anything more about it then you can give them back a similar response and avoid talking about it unless they will do so openly. If you know for sure that it will create a problem at some point, you might want to try to confront them at a good time. Try to impress them with good behaviour before you do and have some arguments ready to make in defence of your use of weed. Tell them that you liking it isnt going to change based on any punishments and offer to prove that you can use it responsibly. Let them know that anything they do to fight it will only distance you from them, and thats not what you want.