Witnesses at Commission proceedings are protected by the provisions of 18 U.S.C. 1505,which,with,evade,prevent,or,in,with,willfully,misrepresents,removes,conceals,covers,destroys,mutilates,alters,or,answers,or,which; or attempts to do so or solicits another to do so; or whoever corruptly, or by threats or force, or by any threatening letter or communication influences, obstructs, or impedes or endeavors to influence, obstruct, or impede the due and proper administration of the law under which any pending proceeding is being had before any department or agency of the United States, or the due and proper exercise of the power of inquiry under which any inquiry or investigation is being had by either House, or any committee of either House or any joint committee of the Congress shall be fined under this title or imprisoned not more than five years, or both.