The Supreme Court has been asked to put on hold an appeals court decision that found the enforcement provisions of a federal anti-doping horse racing law unconstitutional.

If the US Court of Appeals for the Fifth Circuit’s decision is allowed to take effect nationwide, “more horses would die and more cheaters would prosper,” the Horseracing Integrity and Safety Authority Inc. told the justices in its request for a stay Monday.

The private organization is empowered by the federal Horseracing Integrity and Safety Act (HISA) to set and enforce rules for the industry. The Fifth Circuit has twice found the law’s …