In my opinion, this does not dismiss the possibility that Shaw was involved only that the CIA was not directly involved in the assassination. We know that Shaw had some-type of relationship with the CIA and I have to assume that if Shaw was personally involved with the assassination the CIA would have heard about it through the grapevine. In this case, why would the CIA get involved with Shaw's defense? To me, this situation is simular to the case of Barry Seal.
Additionally, if the CIA was directly involved and Shaw was their man, why not just have Shaw killed?
Having said that, I personally feel Garrison was on to something down in New Orleans but I do not believe that Shaw was involved to the degree that Garrison states. I have not seen any creditable evidence showing Clay Shaw was Clay Bertrand.