I also live in an apartment building. The woman who lives above me never leaves her apartment and chain smokes all day. The tenant above her who was asthmatic had to move out because it was coming into her apartment - which stank of cigarette smoke. And in hot weather, her smoke permeates the entire building. I'm gonna show this article to my landlord.
For what purpose?
I rent an apartment and have a small macaw who can be noisy but I monitor her when I'm home and the neighbors don't complain (fortunately, only two apartments directly abut my unit and both have large dogs so they aren't really in a position to beef about it).
My landlady likes my bird (I am clean about it) and so when another woman wanted to rent and said she had birds, the landlady agreed. But this lady had *seven* birds who not only screamed at each other all day but the woman let them poop all over the carpet and ruin the floors which had to be replaced.
I mention this because I think it relates to this smoking issue. Having one dog or one cat is like puffing on one cigarette every couple of hours. Nobody really minds and the landlord would likely go along with allowing it. But if a renter brought in 20 dogs or 20 cats, you now have a problem the landlord has to prevent to protect his property and his other tennants.
I don't see this ruling as precedent-setting as much as I see it as a practical situation. If these smokers are lighting up six cigarettes an hour (as I've seen a smoker do before), they are creating a nuisance that can adversely effect the neighbors. I don't know, in reality, how much the couple smoked but the term "excessive" would mean to me that they were smoking beyond what the ventilation capacity of the apartment could take.
You could ask the smokers to cut down on their smoking but, like asking a pet owner to get rid of half their dogs, I doubt it was received too positively.