U.S. District Court Judge Graham Mullen concluded the "likelihood of a false positive in this case is quite substantial." The decision came after NASCAR's lawyers portrayed Mayfield as a danger to the sport after he tested positive for methamphetamines on May 1. He was suspended indefinitely eight days later.

"This is huge for us. This means more to me probably than any race I've ever won or anything," a smiling Mayfield said outside the courtroom, with his wife, Shana, at his side. "To come out here and do what we did [Wednesday]. ... All the attorneys worked tirelessly and endlessly. It all paid off for us."

Still, Mayfield said he was unsure if he would be able to secure the money needed to bring his car to Daytona. The deadline to enter Saturday's race was June 23. Mayfield, however, still can join the race as a late entry until the garage opens at 8:30 a.m. Thursday though he would not earn any championship points.

Mayfield also suggested he might drive a car for another team and said a decision would be made soon.

"It's kind of late in the game right now, but we're able to go. That was our goal, to be able to go back to work and race cars," Mayfield said. "The main thing is to clear the air and let the fans know. It just feels good to get this off our back, and now we'll move forward."

NASCAR chairman Brian France said the organization has no immediate plans to file an appeal, but he didn't rule it out.

"We're disappointed, but we'll honor the court's wishes. That's where we stand," France said. "I'm not going to comment on what we're going to do yet on the next legal process."

Mullen ruled the "harm to Mr. Mayfield significantly outweighs the harm to NASCAR" in issuing the injunction, which doesn't settle the larger civil suit filed by Mayfield or NASCAR's countersuit.

While addressing NASCAR's concerns of allowing someone who tested positive for an illegal drug back on the track, Mullen said NASCAR can test Mayfield constantly "to determine if he's been a meth-head or not."

"If they want it, I cut it about once a week so we can do that," Mayfield said. "Whatever we've got to do."

NASCAR spokesman Ramsey Poston said if Mayfield attempts to qualify for the race, he will undergo a drug test. Mayfield said he would gladly submit to tests.

Mayfield attorney Bill Diehl argued in court that his client never had the opportunity to challenge the positive test and has never shown any characteristics of a meth abuser. If Mayfield used the drug at the levels NASCAR has suggested, Diehl suggested Mayfield would be "either a walking zombie or he's dead.

In an affidavit filed last week, Mayfield denied ever using methamphetamines and said he didn't know how he failed the May 1 random drug test.

Mayfield has blamed his positive test result on the combination of Adderall for Attention Deficit Hyperactivity Disorder, and Claritin-D for allergies, an explanation repeatedly debunked by NASCAR's program administrator.

But NASCAR attorney Paul Hendrick said the "massive amounts" of methamphetamines in the drug sample indicate Mayfield's claim is a "statement that's simply not true."

Diehl also argued that NASCAR's drug-testing program is flawed because Mayfield never had the opportunity to get his backup "B" sample tested by an independent laboratory. Nashville, Tenn.-based Aegis Sciences Corp., which runs NASCAR's testing program, tested both of Mayfield's samples.

Diehl argued that federal guidelines allow an individual a 72-hour window to have an independent lab analyze a sealed backup sample. He said that when Aegis tested the backup "B" sample two days after the "A" sample came back positive, Mayfield lost any opportunity to challenge the results because the seal had been broken on the second sample.

Hendrick countered that argument, saying the governing body is a private company that does not need to follow the federal guidelines.

"This is not a case about chocolate milk or orange juice," said Helen Maher, another NASCAR attorney. "This is about public safety."

"Who will protect the drivers? Who will protect the fans?" she asked, if Mayfield were allowed back on the track.