U.S. Supreme Court
Walker v. Whitehead, 83 U.S. 16 Wall. 314 314 (1872)
Walker v. Whitehead
83 U.S. (16 Wall.) 314
1. The laws which exist at the time of the making a contract, and in the place where it is made and to be performed, enter into and make part of it. This embraces those laws alike which affect its validity, construction, discharge, and enforcement. The remedy or means of enforcing a contract is a part of that "obligation" of a contract which the Constitution protects against being impaired by any law passed by a state.
2. Held, accordingly, when, on the 1st of January, 1870, suit was brought on a promissory note given in March, 1864, payable in March, 1865, that chanroblesvirtualawlibrary
a law passed in October, 1870, which enacted (by one section) that in all suits pending on any contract made before June 1, 1865, it should not be lawful for the plaintiff to have a verdict unless he made it appear that all taxes chargeable by law on the same had "been duly paid for each year since the making of the same," and enacted (by another section) that it should be a condition precedent to such recovery that "the said debt has been regularly given in for taxes and the taxes paid," and (by other sections) made other retrospective enactments, impaired the obligation of a contract, and was accordingly unconstitutional.