Lawyers for Colorado bar owners say the eight-week-old statewide smoking ban has devastated some smaller taverns, slashing their incomes by up to 80 percent.

In a court filing Friday, the lawyers also said the ban has triggered layoffs and caused fights among patrons who go outside to smoke.

The bar owners are suing in federal court, saying the smoking ban is unconstitutional. They say they're being treated unfairly because they are covered by the ban but casinos are not.

Attorneys for the state also filed motions Friday. They argue that casinos aren't like bars and can be treated differently.

The state also argues the Legislature had valid reasons for exempting casinos, including the 100 million dollars they generate for the state every year.

The ban went into effect July 1. It prohibits smoking in bars and most other public places but exempts casinos, cigar bars that opened before 2006 and the Denver International Airport smoking lounge.

Private workplaces with three or fewer employees are also exempt.