The Horseracing Integrity and Safety Authority (HISA) has spent seven months writing the standards, known as the Anti-Doping and Medication Control (ADMC) program, set to replace a patchwork of state rules to better protect horses.
But a federal appeals court last month ruled unconstitutional the law that creates HISA as it did not give the Federal Trade Commission (FTC) enough oversight of the authority's decisions.
In response, the FTC voted on Monday to deny the draft rules "without prejudice due to current legal uncertainties," Ben Mosier, executive director of the authority's horseracing integrity and welfare unit, said in a statement.
Reuters reported this month that US Senate Republican leader Mitch McConnell of horse-racing stronghold Kentucky was pushing for changes to the law that would satisfy the court to be included into a broader spending bill.
The full-year spending bill, known as an "omnibus," could pass before the year's end.
In response to the report, attorneys general in nine states urged McConnell in a letter to abandon that work, saying the law takes too much power away from states and imposes unreasonable costs.
Reform proponents say the current position is unsustainable and the public will no longer support an industry in which horses routinely perish during training and competition.
Mosier said his group would use any additional time before the eventual implementation to ensure the industry is "even more prepared for an efficient rollout of this program."
"(The program) will promote fair competition in the sport of thoroughbred racing and the safety and welfare of our human and equine athletes," he said.
