Is trading currencies by selling foreign currency exchange receipts on the black market permissible in Islamic law, and what should one do with the money earned from it if the work is forbidden, and is it permissible to spend it on relatives or charities while extracting the principal capital?

If the state prohibits this act due to its circumvention of its conditions, then it is impermissible to perform it, and the state's conditions must be adhered to. As for the money acquired from this transaction, there is no harm in benefiting from it, so long as the currency exchange and sale were conducted according to their legitimate Islamic regulations, despite the sin of disobeying the ruler. It is preferable to present the matter to the scholars of the country due to their knowledge of its affairs.