California Chrome will be allowed to wear a nasal strip in the Belmont Stakes, when he will try to become the first horse in 36 years to win the Triple Crown.
New York was the only state that banned the strips, but on Monday, racing stewards unanimously approved the use of the three-inch wide breathing strips, effective immediately.
California Chrome's trainer said he might not enter the horse in the race if he couldn't wear the strip.
The thoroughbred wore the device in his last six races, which were all victories, including the Kentucky Derby and the Preakness Stakes.
The last horse to win the Triple Crown was Affirmed in 1978.
Since then, 12 horses have won the first two legs but failed to win in New York.