What is the ruling on teaching man-made laws and receiving a salary for that?

It is permissible to teach or study man-made laws to expose their falsehood, distinguish their truth from their falsehood, and clarify the supremacy and perfection of Islamic Sharia. It may even be obligatory if there is a need to establish the truth and abolish falsehood, and it is permissible to take a wage for it.

As for teaching them out of desire for them, promoting them, paralleling them with Islamic legislation, or antagonizing it, this is open defiance of Allah and His Messenger and clear disbelief. Taking a wage for it is illicit gain and evil.