The governing body said the mechanical passive-elastic carbon-fiber blades gave him a leg length of 104 centimeters and a standing height of 184 centimeters, which gives him a competitive advantage over athletes not using such aids.
World Athletics has a Maximum Allowable Standing Height (MASH) rule that prevents disabled athletes from “over-compensating for the absence of a missing limb” and was applied in Leeper’s case.
“The decision means Mr Leeper cannot compete wearing these new RSPs at World Athletics’ major international events… or the Olympic Games,” World Athletics said in a statement on Monday.
Leeper will be allowed to use the blades in other international competitions but his results will not be recognized and they will be listed separately.
In October, Leeper lost his appeal at the Court of Arbitration for Sport (CAS) against a ban on the running blades that allow him to compete with able-bodied athletes, which ended his chances of taking part at the Tokyo Olympics.
Leeper, 31, who was born without legs below the knees, finished fifth in the 400 meters at the U.S. championships in 2019 but was barred from competing at the subsequent world championships in Doha.