So for many years I have been interested in and studying what separates smokers from non-smokers.
Recently I found this article.
Its about cotinine - a metabolite of nicotine (basically nicotine treated with either hydrogen peroxide or UV light).
Most (say 65% or more) of nicotine is converted to cotinine when you vape or smoke cigarettes.
Its says, among much else, that "Individuals that express a catalytically deficient form of CYP2A6 [ a gene ] (i.e., CYP2A6*4) showed a lower rate of cigarette consumption compared with individuals that express the normal allele... Therefore cotinine metabolism and, consequently, smoking behavior can be influenced by ethnicity."
Thus whether or not your body expresses CYP2A6 a certain way determines your reaction to cotinine.
A deficient expression of the gene and you don't need to smoke (I believe I have that) because you process cotinine differently.
Cotinine comes from the nicotine you ingest (non smokers have a very low level in their blood) - either eat, e.g., peppers, or inhale.
Smokers have a much higher level of cotinine in their blood (hence the use of cotinine markers for busting smokers) - but its because genetically they need it.
There is enough meat in this article (plus much else available about cotinine) to convince me smoking (or vaping) is genetic.
Hence discrimination against smokers is like discriminating against women with BRCA (the breast cancer gene).
I would think this is illegal.