No tax is imposed by this section 3-4-4 with respect to any transaction in interstate commerce or otherwise to the extent to which such business may not, under the constitution and statutes of the United States, be made subject to taxation by the state or any political subdivision thereof; nor shall any persons engaged in the business of distributing, supplying, furnishing or selling gas be subject to taxation under the provisions of this section 3-4-4 for such transactions as are or may become subject to taxation under the provisions of the "municipal retailers' occupation tax act" authorized by 65 Illinois Compiled Statutes 5/8-11-1. (Ord. 0-30-09, 10-5-2009)