Delier was taken aback; he hadn't expected that.
Though the police and prison systems appeared closely linked, they were actually independent entities. As Pronto had said, without the warden's consent, no one could see the prisoners. Even dismissing the warden required layers of bureaucratic approval, and by the time those papers passed through, it wouldn't be surprising if a prisoner suddenly "died" along the way. The prison system might not be particularly powerful in the broader social structure, but once you crossed paths with it, you'd feel the weight of the "independent king" authority it wielded.
In prison, inmates often referred to the warden as "His Majesty the King" because every rule and regulation was dictated by the warden alone.
Wardens had near-absolute authority within the prison, but outside of it… they were nobodies, especially when unrelated to their domain.