Associated Press

NASCAR chairman and CEO Brian France answers questions about the Substance Abuse Policy at a news conference at Daytona International Speedway in Daytona Beach, Fla., Friday.

DAYTONA BEACH, Fla. -- NASCAR chairman Brian France passionately defended the sport's drug policy Friday, two days after a federal judge granted Jeremy Mayfield an injunction to compete in Sprint Cup events for the first time since his suspension in May for a failed drug test.

France raised his voice and was as animated as he has ever been in any meeting with media members.

Earlier this week, Judge Graham Mullen questioned the results of Mayfield's drug test, calling the likelihood of a false positive as "quite substantial" during the proceeding at U.S. District Court in Charlotte, N.C.

France said that the Substance Abuse Policy provides for due process for someone who tests positive. France also said there is a list of banned substances but that NASCAR is not limited to it because series officials are focused on anything that can impair a competitor.

"We remain very comfortable ... despite the ruling, that our policy is thorough, it's accurate and it's fair," he said at Daytona International Speedway.

Yet, Mullen questioned one of NASCAR's attorneys during Wednesday's injunction hearing about if there is a limit to the discretion NASCAR has with its policy. As attorney Helen Maher tried to answer the question, Mullen interrupted and said: "That's not a response. If you're answer is none, step up and own it."

Maher said: "It's always up to NASCAR's sole discretion."

France used Friday's media session to explain the lengths NASCAR goes to once there is a positive test. He notes the substance abuse policy has "some built-in flexibilities."

France said that positive tests occur "very, very frequently." He noted that the person is contacted and often is told the dosage of whatever prescription or over-the-counter medicine they are taking needs to be adjusted and they are not penalized.

"Happens all the time," France said.

Mayfield, though, tested positive for methamphetamine. Mayfield's attorneys have challenged some of the testing procedure and Mayfield says he's never taken the drug.

Another topic has been what drugs NASCAR test competitors and officials for. Mayfield's attorney, Bill Diehl, stated in court Wednesday that "they don't have an identifiable list in policy of what is banned."

NASCAR's attorneys submitted only one document that listed any sort of banned substances. That was a letter dated Dec. 8, 2008, sent to teams that detailed what drugs must be tested for when their crew members were tested before the season. The list includes drugs under classifications of amphetamines, narcotics, barbiturates, among other groups.

France said that there is a more exhaustive list.

"It's very lengthy," he said. "It's very scientific in describing a myriad of literally hundreds of drugs, but we also know abuses that could impair you on the race track can also come ... [from] prescription medications. You can abuse a lot of things.

"And there [are] also drugs that we are not aware of that hit the street that are created. So, by definition, we are not going to have an absolute list. With the inherent risk element that we have in the sport, our tests have to be deeper, thorough [and] have a little more flexibility to make sure that we are upholding our responsibility.

"We focus on impairment and impairment can come from the terrible drugs that you know about that are banned and are illegal in society to a misuse of a prescription that in the judgment of our doctors would have impaired [someone]."

Pit stops

Rain canceled qualifying for tonight's Coke Zero 400. Points leader Tony Stewart starts on the pole with Jeff Gordon also on the front row. ... Mike Wallace and Max Papis did not make the race. ... Kyle Busch and Scott Speed will be teammates in this afternoon's Grand-Am race on Daytona's road course. They're driving for one of Chip Ganassi's teams.