It is unlawful for any licensee to sell or keep for sale and/or have on his premises for any purposes whatever, any liquor and/or wine except that purchased from a state liquor store. A licensee found in possession of, or selling and keeping for sale, any liquor and/or wine which was not purchased from a state liquor store shall, upon conviction, be punished as provided in subsection 3-2-15B of this chapter, and if the council shall be satisfied that any such liquor and/or wine was knowingly sold or kept for sale within the licensed premises by such licensee or by his agents, servants or employees, it shall be mandatory that the city council immediately revoke the license of said licensee. (1975 Code § 5.08.100)