It shall be unlawful for any person within the corporate limits to use or employ any building or premise, now or hereafter erected, or existing in this Municipality, as a stockyard, animal weighing pen, whether temporarily used for weighing, loading or unloading during transportation or not, or as a commercial cattle, hog, sheep, or animal feed lot, or to use or employ buildings, sheds or pavilions used as interior sales barns without the previous permission, in writing, of the Governing Body. Nothing herein shall apply to any person now operating within the corporate limits a commercial sale barn, stockyard, or animal weighing pen, or who presently uses or employs buildings, sheds or pavilions as interior sale barns, but shall apply to any assignee of such person.