The injunction was filed Tuesday in Buchanan County court on behalf of Steve Peterman, owner of the Shamrock on St. Joseph Avenue.
The suit claims, in part, that the ban violates the state constitution by treating businesses unequally.
The smoking ban exempts the St. Jo Frontier Casino from the law.
The ordinance, passed by voters earlier this month, bans smoking in bars and restaurants but still allows for smoking on the casino floor.
Under the ordinance, the casino would remain exempt from the smoking ban unless smoking is also banned in nearby casinos in Missouri and Kansas.
The lawsuit argues that the St. Jo Frontier Casino is an "enclosed public place", as defined by the ordinance, and is no different in this regard than the Shamrock.
It claims that the casino is being granted special rights.
"The only difference between the Shamrock and the gaming area of the St. Jo Frontier Casino as to the subject of the Ordinance is the St. Jo Frontier Casino is owned by a large corporation with more political power than Plantiff, a one member LLC," states the lawsuit.
The smoking ordinance goes into effect June 7.
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