Article I, Section 10, Clause 1:
No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility.
private contract is, naturally, not all-inclusive. A judgment, though granted in favor of a creditor, is not a contract in the sense of the Constitution, 1 nor is marriage. 2 And whether a particular agreement is a valid contract is a question for the courts, and finally for the Supreme Court, when the protection of the contract clause is invoked. 3
The question of the nature and source of the obligation of a contract, which went by default in Fletcher v. Peck and the Dartmouth College case, with such vastly important consequences, had eventually to be met and answered by the Court in connection with private contracts. The first case involving such a contract to reach the Supreme Court was Sturges v. Crowninshield, 4 in which a debtor sought escape behind a state insolvency act of later date than his note. The act was held inoperative, but whether this was because of its retroactivity in this particular case or for the broader reason that it assumed to excuse debtors from their promises was not at the time made clear. As noted earlier, Chief Justice Marshall's definition on this occasion of the obligation of a contract as the law that binds the parties to perform their undertakings was not free from ambiguity, owing to the uncertain connotation of the term
These obscurities were finally cleared up for most cases in Ogden v. Saunders, 6 in which the temporal relation of the statute and the contract involved was exactly reversed – the former antedating the latter. Chief Justice Marshall contended unsuccessfully that the statute was void because it purported to release the debtor from that original, intrinsic obligation that always attaches under natural law to the acts of free agents.
When, he wrote,
we advert to the course of reading generally pursued by American statesmen in early life, we must suppose that the framers of our Constitution were intimately acquainted with the writings of those wise and learned men whose treatises on the laws of nature and nations have guided public opinion on the subjects of obligation and contracts, and that they took their views on these subjects from those sources. He also posed the question of what would happen to the Contract Clause if states might pass acts declaring that all contracts made subsequently thereto should be subject to legislative control. 7
For the first and only time, a majority of the Court abandoned the Chief Justice's leadership. Speaking by Justice Washington, it held that the obligation of private contracts is derived from the municipal law – state statutes and judicial decisions – and that the inhibition of Article I, § 10, is confined to legislative acts made after the contracts affected by them, subject to the following exception. By a curiously complicated line of reasoning, the Court also held in the same case that, when the creditor is a nonresident, then a state by an insolvency law may not alter the former's rights under a contract, albeit one of later date.
With the proposition established that the obligation of a private contract comes from the municipal law in existence when the contract is made, a further question presents itself, namely, what part of the municipal law is referred to? No doubt, the law which determines the validity of the contract itself is a part of such law. Also part of such law is the law which interprets the terms used in the contract, or which supplies certain terms when others are used, as for instance, constitutional provisions or statutes which determine what is
legal tender for the payment of debts, or judicial decisions which construe the term
for value received as used in a promissory note, and so on. In short, any law which at the time of the making of a contract goes to measure the rights and duties of the parties to it in relation to each other enters into its obligation.