Is it permissible to transport undocumented individuals (those without papers) within the Kingdom from one city to another, and is the money received from them lawful or unlawful?

If the ruler prohibits a permissible act for a clear, general, legitimate interest, and a clear harm results from violating his prohibition, then it is not permissible to violate it, neither outwardly nor inwardly. Therefore, if your husband is transporting in violation of this law, it is not permissible to do so, and it appears that the wages are unlawful. He must dispose of them unless he is poor and in need of them.