LONDON — Track and field’s world governing body ruled on Monday that Oscar Pistorius, a double-amputee sprinter from South Africa, is not be eligible to compete in Olympic qualifying events. The International Association of Athletics Federations explained in a statement that, after an independent scientific study, it deemed Pistorius’s state-of-the-art carbon fiber prosthetics “should be considered as technical aids which give him an advantage over other athletes not using them.”

Pistorius’s agent, Peet Van Zyl, said that he and Pistorius were seeking legal advice in order to prepare an appeal. “We need to speak with the I.A.A.F. first and see what approaches...