The Supreme Court has rejected a challenge from Republican-controlled states to a horse racing safety law that has led to national medication and anti-doping rules.

Churchill Downs will suspend racing operations on Wednesday and move the remainder of its spring meet to Ellis Park to conduct a “top-to-bottom” review of safety and surface protocols in the wake of 12 horse fatalities the past month at the home of the Kentucky Derby.

Trainer Bob Baffert says Kentucky Derby winner Medina Spirit was treated with an antifungal ointment containing the steroid betamethasone that may have caused the horse to fail a postrace drug test.