Restaurants might not have to put away their ashtrays Friday.

A group of local business owners on Tuesday filed a challenge in District Court to the constitutionality of Question 5, the anti-smoking initiative voters approved in November. The new smoking restrictions are slated to take effect Friday.

But attorneys with the law firms of Jones Vargas and Campbell & Williams are hoping Judge Douglas Herndon will grant a temporary restraining order or an injunction placing the Nevada Clean Indoor Air Act on hold while the court weighs the merit of the arguments against the new law.

"If we get the TRO (temporary restraining order), that's going to buy some time until the court determines whether the statute is constitutional or not," said Kirk Lenhard, one of the attorneys handling the complaint for 20 local businesses. "If the TRO is denied, all (businesses) face compliance starting Friday morning, whatever that (compliance) means, by the way. I've got seven years of higher education and I'm not sure what it means."

The complaint filed Tuesday states that the statute "is impermissibly vague" about what conduct is criminalized and therefore violates the plaintiffs' constitutional right to due process.

Lenhard emphasized that business owners still do not know who is going to enforce the law, which includes a penalty of up to six months in jail or a $1,000 fine.

The statute allows smoking in standalone bars as well as casinos and other businesses with unrestricted gaming licenses. Opponents of the new law complain that creates an uneven playing field for businesses that compete with standalone bars, casinos and other businesses with unrestricted gaming licenses, but unlike them will be forced to be smoke-free. The lawsuit states that the new law "arbitrarily distinguishes between similarly situated entities without rational relation to a legitimate government interest" and therefore violates the plaintiffs' constitutional right to equal protection.

The request for a temporary restraining order cites the example of Village Pub & Poker Entities, which operates under a restricted gaming license but has the same square footage and business operations as taverns with nonrestricted licenses, which have 16 or more gaming devices. The act treats these two types of locations differently, allowing nonrestricted licensees to permit smoking and serve food under the "casino" exception, according to the document.

The lawsuit also notes that the stated purpose of the new statute is "to prevent children and families from being exposed to secondhand smoke," and yet it would still allow smoking in some places where children and families are allowed.

University of Nevada, Las Vegas, law professor Lynne Henderson, who teaches constitutional law, says she has seen similar arguments made in other states.

"One of the things that's troubling is that large casinos are exempt and it will hurt smaller businesses, but this (type of challenge) has not worked for anybody in any other state, so I'm not sure what success they're going to have," Henderson said of the businesses seeking the injunction.

Likewise, advocates for the act noted that challenges to similar statutes in other states have been unsuccessful.

But Lenhard countered that those states' statutes defined enforcement procedures and were crafted by state legislatures. This act appears to be "haphazardly" thrown together, he said.

Henderson said the plaintiffs have very good lawyers working for them. Ronald Rotunda, a professor of law at George Mason University in Virginia is one of the leading constitutional attorneys in the country and one of the lead attorneys filing the complaint. Rotunda declined comment about the details of the suit, saying he'd prefer to speak after the parties file briefs.

Henderson, however, said she does not believe the act violates the equal protection clause of the constitution.

"The voters can deal with a problem a step at a time, so if they want to forbid smoking in grocery stores with restricted gaming licenses, it doesn't violate equal protection not to extend it to unrestricted gaming licenses," she said. "It's a long-standing equal protection doctrine that the Legislature can solve a problem a step at a time. It doesn't have to be a perfect fit unless it involves a very important right such as racial discrimination."

The businesses will still be able to operate, she said, adding that she did not believe it was difficult to determine how to comply with the statute.

It was unclear Tuesday when Herndon would conduct a hearing on the matter, but Lenhard said he's confident Herndon will squeeze it in before Friday.

The defendants mentioned in the suit are law enforcement and health district officials, many of whom refused to comment Tuesday about the complaint.

State Attorney General George Chanos issued a statement saying he will work with the codefendants, including Sheriff Bill Young, District Attorney David Roger and Henderson, North Las Vegas and Las Vegas officials, to implement the lawful intent of voters.

Buffy Martin-Tarbox, the government relations director for the American Cancer Society and the spokeswoman for Nevadans for Tobacco Free Kids, which advocated for Question 5 but was not mentioned in the suit, said it's disappointing some business owners are doing their best to "skirt" the will of voters.

The ballot initiative, "has been given the OK by two different courts in the state of Nevada, including the Nevada Supreme Court, so we know that it's a solid law," she said, referring to a 6-1 Supreme Court decision in September that upheld the smoking restrictions on the ballot.

But the Supreme Court ruling did not explicitly uphold the statute language itself. Instead, it found that the challenge to the ballot initiative was premature. "Attacks based on the alleged constitutionality of the measure, if it were passed, are not appropriate for pre-election review," the court stated.

The Nevada Tavern Owners Association, which rallied members against Question 5, is not a party to the lawsuit. Geno Hill, the association's president and operator of the Rum Runner tavern, said the group is still exploring its own legal options.

Hill said he will halt food service at the Rum Runner if the new smoking restrictions take effect

Other taverns owners were noncommittal. If an injunction is not in place by Friday, tavern operators could be faced with one of two choices -- eliminate smoking or eliminate food service.

Sean Higgins, who operates Three Angry Wives Pub with his brothers, wouldn't say Tuesday whether the pub would take either option. Three Angry Wives is a plaintiff in the lawsuit and Higgins is general counsel for Herbst Gaming, one of the primary forces against Question 5. Herbst, through its Terrible Herbst convenience stores and gasoline stations, supported the defeated Question 4, the less restrictive of the smoking measures.

"We just want to see how this (TRO request) plays out before we make a decision," Higgins said.

Ron Drake, who operates the Point After Lounge and is an active member of the Tavern Owners Association, was also unsure what direction he would take if the injunction isn't granted. He said the Clark County Health District has not provided tavern owners with any guidance as Friday approaches.