If any clause, sentence, paragraph, or part of this subchapter, which shall be known by the short title of the Migratory Bird Treaty Act, shall, for any reason, be adjudged by any court of competent jurisdiction to be invalid, such judgment shall not affect, impair, or invalidate the remainder thereof, but shall be confined in its operation to the clause, sentence, paragraph, or part thereof directly involved in the controversy in which such judgment shall have been rendered.