On the contrary! It is the adopted sonship that is the free gift. The obedience is our response to that free gift. My obedience (what little there could possible be) is worthless outside of being Christ's adopted brother, but IS of value when performed by a member of His family. I suspect that this is the answer to the dilema some have reconciling James 2 with Paul's doctrine of Faith.
Since you ignored my analogy of the Christmas gift (I'd still like an answer to that), I'll use yours. If you had an adopted son and he disobeyed you, would you reject him and kick him out of the family or just discipline him to teach him the right way? The RC way, making the gift of sonship at all conditional on obedience, means he is out of the family.