Service of Gd means that you live your life in total dedication to Gd. Everything that you do is an expression of His will. Living in the service of Gd therefore requires active recognition of Gd and reference to His authority in decision making. In every action of your day you consider the laws and principles of the Torah as well as the will of Gd before reaching a decision on how to behave.
Free will lies in the degree to which you are able to enforce this awareness.
Idolatry is service of another entity in place of Gd, and places that other entity in a position of greater authority in your life. Idolatry is distinguished by any state in which the determining factor of your actions is anything other than the will of Gd. Physiological or psychological addictions cause your behaviour to be determined by a substance to which your will has become subject. Any substance which alters your mind from a state of being able to focus cognitively on the subjugation of your own will to Gd's in your actions, for however brief a period of time, is idolatrous. It is for this reason that emotions which subvert the capacity of the mind; such as anger, pride, and jealousy; are compared to idolatry. They remove man from having free will, without which he cannot serve Gd.
Most people forbid drugs and smoking on the grounds that they are unhealthy and therefore constitute a violation of the Biblical commandment of 'וְנִשְׁמַרְתֶּם מְאֹד לְנַפְשֹׁתֵיכֶם' 'and you shall very closely guard your lives.' There is also the stance that drugs are prohibited by Torah inasmuch as they are prohibited by American law and the Torah requires us to obey the law of the land.
I affirm that smoking, or taking drugs, or even simply becoming drunk constitute a violation of nothing less than "you shall not have other gods before Me."
24 Nissan 5773