DAYTONA BEACH, Fla. (AP) — Brian France defended NASCAR’s drug testing policy as the toughest in professional sports, despite a federal judge’s ruling that overturned driver Jeremy Mayfield’s suspension.

Mayfield was indefinitely suspended May 9 for what NASCAR said was a positive test for methamphetamines. He sued to be reinstated, and a federal judge issued an injunction Wednesday that allowed Mayfield to return to competition based on Mayfield’s argument that NASCAR’s testing system is flawed.

U.S. District Court Judge Graham Mullen questioned the test results, saying the possibility of a false positive was “quite substantial” and ruled the harm to Mayfield significantly outweighed the harm to NASCAR.

But NASCAR’s chairman said the sport needs a tough system that bans impaired drivers from competition.

“We remain very comfortable and very calm despite the ruling, that our policy is thorough, it’s accurate, and it’s fair,” France said Friday at Daytona International Speedway, site of Saturday night’s race.

“It’s our responsibility to protect the drivers, the fans, other participants within the events. We have a very unique challenge relative to all sports, which is the inherent danger of somebody impaired on the racetrack.”

Mayfield did not enter his car to race in Saturday night’s event and would now only be able to compete as a NASCAR-approved relief driver. Although he said after the ruling he would travel to Daytona this weekend, he had yet to claim the credential needed to enter the garage area.

France said NASCAR is still exploring its legal options concerning the injunction. The civil suit filed by Mayfield and NASCAR’s countersuit still remain.

But the chairman insisted NASCAR intends to defend its drug testing policy “very vigorously.”

“Our first responsibility, despite the ruling on Wednesday or any ruling, will always be that we are going to make sure every way we can that everyone who is driving these race cars are of clear mind,” France said. “We don’t just go laying the hammer down and ruining someone’s career. That’s not what we are talking about when we are talking about Jeremy’s situation.

“You know what he was tested for. That’s unequivocal. There’s no confusion about that from a science standpoint.”

Mayfield has denied using methamphetamines and blamed the positive test result on the combined use of Adderall for Attention Deficit Hyperactivity Disorder and Claritin-D for allergies. That result was debunked by NASCAR’s drug testing administrator.

“We know what it means, to anyone, to get such a positive test back,” France said. “We are very comfortable that that test is accurate and reliable and will hold up, ultimately, when all of the facts are heard.”

Mayfield’s lawyers focused on federal guidelines that allow an individual a 72-hour window after a positive test to have the backup “B” sample analyzed by an independent laboratory. Because NASCAR’s commissioned laboratory tested both of Mayfield’s samples, lawyer Bill Diehl blasted the fairness of a process that did not give Mayfield the opportunity to challenge the results.

France, who took questions on the issue for about 45 minutes with NASCAR president Mike Helton and several top series officials watching from the back of the room, insisted NASCAR has a series of checks and balances in its testing process that prevents wrongful persecution.

“We had to have the toughest policy because we have the most to lose if one of our players is on … the track impaired,” France said. “We know we came up with a very good policy. People frequently test positive for one thing or another. It happens very, very frequently. It’s very rare, though, that we do a suspension, because that’s a very serious matter.

“We realize the seriousness and implications that has to an individual, to a race team, to their careers. It’s why the policy has some built-in flexibilities.”

Among them are allowances for prescribed medications taken as directed, but NASCAR makes it each individual’s responsibility to keep officials informed of changes in health. In court documents filed before Wednesday’s hearing, NASCAR alleged Mayfield never informed anyone he was taking Adderall.

France also said he’s surprised at the confusion Mayfield’s suspension has created, and questions of fairness about a tough policy meant to protect its participants.

“At some point when you have a positive test, it should be the end of the road,” he said. “In our judgment, that some point is when your “B” sample comes back unequivocally and conclusively positive for a banned substance that impaired you in the doctors’ and medical experts’ eyes. That is our basic responsibility.”