LAS VEGAS, Nev. -- The middleweight title fight between Chris Weidman and Vitor Belfort is already being hyped by UFC officials as one of the biggest pay-per-view events of the year, but the proposed Memorial Day or July 4th event faces a significant hurdle if it's to be staged in Las Vegas because the 36-year-old Belfort needs clearance from the state athletic commission for an exemption to continue his use of testosterone-replacement therapy.

Dr. Timothy Trainor, consulting physician to the Nevada State Athletic Commission, told "Outside the Lines" Tuesday he would advise the five-member commission against granting a therapeutic-use exemption to Belfort or any fighter who previously tested positive for a performance-enhancing substance. Belfort tested positive in 2006 for 4-Hydroxytestosertone, an anabolic steroid, and was suspended nine months and fined $10,000 by the Nevada commission.

"If we know beyond a shadow of a doubt that someone has used PEDs in the past, they will not get an exemption,'' said Trainor, who is not a voting member of the commission. "No, no way.''

The instance of low testosterone in young, healthy men is minimal, though medical experts claim one cause can be prior steroid usage. Thus, TRT has become a hot topic in the MMA world, where it's perceived as fighters gaming the system and, in some instances, benefiting from prior doping.

Belfort claimed in 2006 that his use of an over-the-counter supplement likely caused his positive test. During a commission meeting, he also raised the possibility it could have been triggered by treatment received following knee surgery six months earlier, and provided a letter from a Brazilian endocrinologist who claimed to have injected him with testosterone.

Asked specifically about Belfort's anticipated TUE request in light of his failed test, Trainor -- who began consulting with the commission in 2007 -- told "Outside the Lines": "Well, it is going to get denied then. If we know for sure he has used steroids in the past, it is going to get denied. ... We're not going to give people a free pass because they admitted they used steroids in the past.''

Commission chairman Francisco Aguilar cautioned, however, that a prior failed drug test is not an immediate disqualifier and that any request from Belfort would be heard and decided upon by the full five-member commission, with input from Trainor. As of Tuesday, Belfort (24-10 MMA, 13-6 UFC) had not filed for a license or TUE exemption for his tentative fight with reigning champion Weidman, though Nevada officials anticipate he'll soon do so.

Aguilar said he would rely on information provided by the commission's medical doctor, but that he would enter any discussions with an open mind and also cognizant of the title fight's importance to Nevada and the reluctance to lose the potential payday to another state. "The economic development impact to the state could be huge,'' he said.

As point of fact, Aguilar said the UFC transferred to the state general fund almost $500,000 just in ticket sales and pay-per-view taxes from the Dec. 28 Weidman-Anderson Silva title fight. The tax figure from all fight cards last year was more than $5 million, he said. The estimated non-gaming impact to the venue hosting a boxing title fight (no figures are known for MMA) exceeds $11 million, according to Las Vegas convention officials.

"There are always people with an interest from the economic perspective, but we also have the obligation and duty to be regulators,'' Aguilar said.

Speaking to safety concerns, commission member Pat Lundvall noted, "The last thing you want is one fighter stepping in a ring that is juiced more than the other. It gives him an unfair advantage and you run into the safety issues.''

Concerned about safety and dangers of steroid use in boxing and mixed martial arts, the Association of Ringside Physicians issued a "consensus statement'' Monday, calling for the elimination of exemptions for testosterone replacement therapy in combat sports. That further puts Nevada officials on the spot as it anticipates Belfort's request.

After the statement was released, Dr. Trainor reiterated to the Nevada Athletic Commission chairman that he would oppose any request by Belfort, saying in an email to Aguilar: "I am not planning on approving a testosterone TUE for Belfort if he applies for it, given his positive steroid test in the past.''

Amid swirling rumors about Belfort, the UFC first issued a statement last February saying he had been on a medically approved TRT regimen under the supervision of a Nevada physician, after having been diagnosed with hypogonadism, or low testosterone. During a recent interview at his training camp in Boca Raton, Fla., Belfort told "Outside the Lines" he's been treated with testosterone replacement therapy for at least the past three years.

"TRT is a treatment,'' Belfort said. "I have a lack of hormones in my body. And I have a doctor. I go to tests [before] every fight.''

"I had low testosterone, and it was making me feel tired and lethargic,'' he added. "They did a bunch of tests. And they discovered I have the issue.''

In the midst of a career rebirth, Belfort, dubbed "The Phenom,'' has won eight of his last 10 fights, losing only to Silva and Jon Jones -- widely regarded as two of the sport's top pound-for-pound fighters. His last five fights have been staged outside the country, including four in his native Brazil. The Brazilian commission and medical director Dr. Marcio Tannure, who also oversees medical activities in the country for the UFC, have allowed Belfort to fight under TRT.

Both Tannure and officials of the Las Vegas-based UFC declined interview requests, though UFC boss Dana White previously has said Belfort should be allowed to fight in Nevada with an exemption for testosterone.

Belfort isn't chatty when the conversation turns to the testosterone issue, either, though he expressed confidence in being able to convince Nevada officials to grant him an exemption -- though that was before Dr. Trainor said he would advice against it, if he were to apply, based on his prior failed drug test.

"You can [be granted an exemption] if you show them you have issues," said Belfort, citing the case of fighter Chael Sonnen. "You had problem [positive test] before. It is just like I pay for something before ... you can't judge twice. You cannot do double jeopardy, you know what I mean. You can not judge me for something I did before."

Reporter Joshua Gross contributed to this report."