Congress may alter, amend, add to, or repeal any of the provisions of sections 41 to 46, 48, 50, 51 to 53, and 54 to 57, of this title; but no contract or individual right made or acquired under such provisions shall be thereby divested or impaired.
R.S. § 5594 derived from act Aug. 10, 1846, ch. 178, § 11, 9 Stat. 106.