WASHINGTON (AP) — The Supreme Court on Monday rejected a challenge from Republican-controlled states to a horse racing safety law that has led to national medication and anti-doping rules.

The justices left in place an appeals court ruling that upheld the law and rejected claims that Congress gave too much power to the Horseracing Integrity and Safety Authority, the private entity that administers the rules.

Charles Scheeler, chairman of HISA's board of directors, cited a 38% decline in equine fatalities for the first three months of this year in applauding the court's decision.

"HISA's uniform standards are having a material, positive impact on the health and well-being of horses," he said in a statement.

Oklahoma, Louisiana and West Virginia sought to have the law struck down, joined by several racetracks.

"I've said all along that we are going to do our due diligence all the way to the U.S. Supreme Court to ensure that the rules governing horsemen are fair, clear and constitutional," said Eric Hamelback, CEO of the National Horsemen's Benevolent and Protective Association.

Both Scheeler and National Thoroughbred Racing Association president and CEO Tom Rooney urged HISA opponents to end their litigation.

"It is long past time for opponents of HISA to drop their outstanding lawsuits," Scheeler said. "In light of this decision, continued litigation only serves to take time and valuable resources away from our core mission of improving the safety and integrity of thoroughbred racing."

Rooney added, "It is time for all parties to stop their internal fighting and support HISA as the law of the land."

The anti-doping program, which took effect in the spring of 2023, is an attempt to centralize the drug testing of racehorses and manage the results, as well as dole out uniform penalties to horses and trainers instead of the previous patchwork rules in the 38 racing states.

"This decision will allow HISA to continue its work to protect the health and safety of equine athletes, thereby fostering greater confidence and integrity in the sport of thoroughbred racing," Rooney said in a statement.

Legislation to dismantle the new authority was introduced in September in the House of Representatives but hasn't gone anywhere.

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