Is money taken in exchange for the recovery of a usurped right, which is neither religiously nor legally permissible, considered lawful or unlawful?

We understand that the questioner assists the oppressed in reclaiming their rights. If that is the case, then it is not permissible for him to take a fee unless he needs expenses for livelihood, or for his efforts, or for travel. In such cases, it is permissible for him to take his expenses and a fair wage (اجرة المثل) without any increase.