Any person other than an Indian of the full blood who shall attempt to reside in the Indian country, or on any Indian reservation, as a trader, or to introduce goods, or to trade therein, without such license, shall forfeit all merchandise offered for sale to the Indians or found in his possession, and shall moreover be liable to a penalty of $500: Provided, That this section shall not apply to any person residing among or trading with the Choctaws, Cherokees, Chickasaws, Creeks, or Seminoles, commonly called the Five Civilized Tribes, residing in said Indian country, and belonging to the Union Agency therein: And provided further, That no white person shall be employed as a clerk by any Indian trader, except such as trade with said Five Civilized Tribes, unless first licensed so to do by the Commissioner of Indian Affairs, under and in conformity to regulations to be established by the Secretary of the Interior.