First, let's establish some guidelines here: You are his parent and in that role you take on certain key responsibilities regarding his physical, emotional, and spiritual welfare. He is 14 and is engaging in illegal activity. This is not about your drug use -- addictive or recreational -- it's about your son's impressionable, peer-influenced, confused mind, body, and well-being.
If you believe that you have no right as a parent to advise your child against any potentially dangerous activity that he is engaged in because you are or have been engaged in it, then you have abdicated your role as a caring parent. Too harsh? I don't think so. I have counseled far too many adolescents in therapy who have told me that they wish their "Sixties parents" had not been so "cool" about their drinking and drugging. They wish their parents had talked with them and given them some guidelines, advice, and limits about drug-taking rather than adopting the attitude of, "Hey we did drugs (are doing drugs) and we're fine -- you'll be fine too."
I don't know why you use drugs and I am not going to engage in self-righteous condemnation of your drug use. But I will remind you that your son does not have the breadth of life experience or drug-taking experience that you do and cannot be expected to make decisions in this regard that are in his best interests. He needs your help in this area and if he is coming home high and allowing you to see him in this state, then he's sending you a message. Take his cue: Please see a therapist yourself about your confusion on this issue and then be the parent that your son needs. If you are going to use this same standard with any and all of your son's actions and behaviors, he's unfortunately going to have an adolescence that will be far more scary and dangerous than needs be.