Once a law is passed, the executive may or may not enforce, the judiciary may or may not try, and the jury may or may not convict, and having convicted, may or may not sentence. Only the jailer has the duty to do what he is ordered to do - that's the separation of powers.
I believe even a jailer has, within some limits, the power to release as they see fit. Not a guard but rather the civil magistrate who administers the jail, such as a Sheriff etc.
I believe you are quite correct in your separation of powers argument.
I disagree. Even the jailer may find himself the last resort. Just as anyone who dares to stand up for what is right may be punished by the system, he runs a risk. But he has a part to play, as do we all.
Even a private in the Army has an obligation to disobey illegal orders or face trial later for executing illegal orders. As you said, the "I was only following orders" defense doesn't work anymore.
Basedon that, it would seem inexcusaable for an AG to defend or execute anti-Constitutinal laws.