The Consequence Argument is one of the main reasons that compatibilism (the idea that determinism and free will are compatible) is almost dead in the realm of philosophy. Here is a simple, non-technical version of the argument. Let's assume determinism is true:
1. No one has power over the facts of the past and the laws of nature (and perhaps the decree of God).
2. No one has power over the fact that the facts of the past and the laws of nature (and perhaps the decree of God) entail every fact of the future (i.e., determinism is true).
3. Therefore, no one has power over the facts of the future.
This argument has nearly killed compatibilism, because without being able to assert that we have power over the future, a compatibilist has no basis upon which to draw a distinction between a free act and an unfree act.
Hence, divine determinism is not compatible with free will.