People rehab for an addictions, and you can be addicted to many, many substances and habits. Addiction is a physical change in brain chemistry and response to stressors. It's unfortunate that he has an addiction, from which he may or may not recover, but you simply cannot say that he's not addicted to using "weed" unless you know him personally. Your post is one of the many perpetuated myths of drugs in this country. You may be accidentally referring to a Physical Dependence though.
http://en.wikipedia.org/wiki/Addictive_behavior
