Is it permissible to take medication obtained through irregular means, knowing that this medication is designated only for citizens of the state, and that there is a previous fatwa that permits its use out of necessity for healing?

If the physician is not authorized to dispense medication to non-citizens, then it is not permissible to take it, and it must be returned to the entity from which it was dispensed or to the physician to return it to that entity. This is because the physician is a private employee and an agent, and he is not permitted to act except within the limits of what his employer has authorized him to do.