Is it permissible to work in the enforcement of man-made judicial rulings?

Man-made laws are divided into two categories: The first is what contradicts and opposes the Sacred Law (Sharia), which is an act of disbelief (kufr), and it is not permissible to assist in it in any way, because that is aiding in sin and transgression. The second is what does not contradict Islamic law; in this case, it is permissible to rule by it and work to disseminate and implement it. However, if the laws contain both truth and falsehood, it is not permissible to act upon them. And whoever abandons something for the sake of Allah, Allah will replace it with something better for him.