16 U.S.C. § 18e
Section, act June 28, 1941, ch. 259, §1, 55 Stat. 350, exempted national park, etc., admission fees from all Federal tax on admissions. Act Sept. 20, 1941, was made effective on, and applicable only with respect to, the period beginning with Oct. 1, 1941, by section 550(a) thereof.