Under "Background" your premise is that "The observed differences in tobacco control policy effectiveness and why policies do not help all smokers are largely unexplained." And then go on to seemingly presume that the answer must be rooted in biology which itself can only take shape on the predication "who wouldn't quit smoking but those who are biologically defective?" "Defective" (or also described as absent "protection" of a gene -- a detriment) strongly implied by the subsequent solution to "fix" it with: "...pharmacological treatments for current smokers who may be unresponsive to major health policy interventions, such as tobacco taxation.") Treatment by definition means to fix what is bad.

And so I offer an alternative explanation -- free will -- for the "unexplained" that is rooted in psychology instead of biology and ask if that confounder was accounted for? Otherwise it would appear that research in this area considers that incomprehensible.