I'm not sure why you need a lawyer and why CKC would have the audacity to facilitate a transfer of stolen property (after all she was taken without your permission as an equal party to her ownership). This seems very simple to me. You know where she is... you have her registration papers. Small claims court for the value of your interest in her and her progeny or her release to your custody. CKC is just a registration body, they have no say over who property belongs to and for what value.
From what I understand with co-owns, one owner can not be forced to give the dog to the other. I know someone else who lost their dog due to the co-owner taking her at a show and refusing to give her back. AKC generally will not sign a co-own over to one owner due to a dispute though.
As far as suing for her and her puppies value, I think that would depend a lot on the nature of the co-own contract. If the dog in with a "foster" home when the co-owner took her, I think he could very well claim that the dog was abandoned by the other owner.
Co-ownerships can get ugly