Matthieu Reeb who is the general secretary for the CAS said that the case could only be heard if an appeal was either part of the Football Association's rules or both parties had agreed in writing to further arbitration.
Reeb said: "If the English FA rules did have a specific clause allowing an appeal to CAS in a case like the Tevez one, there would be no need for both parties to agree to have the case refereed.
"But if there is nothing in the rules, it is mandatory that both parties agree in writing to go to CAS."
FA Chairman Lord Triesman commented: "If it is going to go through the courts it is going to drag on, and on, and on. It would be much simpler for people to observe the rules of football. The FA is a pretty decent regulatory body and there is no reason why a very big club shouldn't feel that it should regard those rules too."
The Hammers' do have some light at the end of the tunnel though as they have the backing of some of the top sports lawyers.