After June 26, 1946, no person shall have authority to permit citizens of the American Republics to receive instruction at the United States Military Academy under the provisions of section 221 of this title. Any person who is receiving instruction at the United States Military Academy on June 26, 1946, under authority of section 221 of this title, may, in the discretion of the President, be permitted to continue to receive such instruction and, if so permitted, shall thereafter be deemed to be receiving instruction under the provisions of section 347 of title 10.