Nothing in this article shall be construed as requiring interstate carriers to make a showing of “public convenience and necessity” in order to secure any license required by the provisions hereof, and the provisions of this article shall apply to interstate commerce only insofar as such regulation is permitted by the Constitutions of Oklahoma and the United States, and the holding of any part of this article or any section or part thereof to be void or ineffective for any cause by any court shall not affect any other section or part of this article.