( CNN) The Olympic Games are set to start in just hours and there's one big question that remains unanswered — which Russian athletes will be allowed to compete?

Part of the International Olympic Committee's ban on Russian athletes — specifically, the decision to bar any Russians from competitor who have been caught for doping but accepted penalty and complied with sanctions — is “unenforceable, ” according to the Court of Arbitration for Sports( CAS ).


Drug testers warn dopers they will be caught eventually