Did you sign any adoption papers at all? Did the rescue sign the dog over to you? I wonder if the rescue can still claim ownership of the dog without anything on paper saying that you adopted the dog.
I'm not sure how all the legalities apply here - but I don't think that they can approach you after six months and ask you to sign a contract that you don't agree with AFTER you got the dog.
BH, OB1, TR1, AD
Rottweiler/Hairy Dog mix?? Shelter rescue
Gryffon Vom Wildhaus