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.
From a different point of view, the Court has sought to distinguish between grants of privileges, whether to individuals or to corporations, which are contracts and those which are mere revocable licenses, although on account of the doctrine of presumed consideration mentioned earlier, this has not always been easy to do. In pursuance of the precedent set in New Jersey v. Wilson, 1 the legislature of a state
may exempt particular parcels of property or the property of particular persons or corporations from taxation, either for a specified period or perpetually, or may limit the amount or rate of taxation, to which such property shall be subjected, and such an exemption is frequently a contract within the sense of the Constitution. Indeed this is always so when the immunity is conferred upon a corporation by the clear terms of its charter. 2 When, on the other hand, an immunity of this sort springs from general law, its precise nature is more open to doubt, as a comparison of decisions will serve to illustrate.
In State Bank of Ohio v. Knoop, 3 a closely divided Court held that a general banking law of Ohio, which provided that companies complying therewith and their stockholders should be exempt from all but certain taxes, was, as to a bank organized under it and its stockholders, a contract within the meaning of Article I, § 10. The provision was not, the Court said,
a legislative command nor a rule of taxation until changed, but a contract stipulating against any change, from the nature of the language used and the circumstances under which it was adopted. 4 When, however, the State of Michigan pledged itself, by a general legislative act, not to tax any corporation, company, or individual undertaking to manufacture salt in the state from water there obtained by boring on property used for this purpose and, furthermore, to pay a bounty on the salt so manufactured, it was held not to have engaged itself within the constitutional sense.
General encouragements, the Court wrote,
held out to all persons indiscriminately, to engage in a particular trade or manufacture, whether such encouragement be in the shape of bounties or drawbacks, or other advantage, are always under the legislative control, and may be discontinued at any time. 5 So far as exemption from taxation is concerned the difference between these two cases is obviously slight, but the later one is unquestionable authority for the proposition that legislative bounties are repealable at will.
Furthermore, exemptions from taxation have in certain cases been treated as gratuities repealable at will, even when conferred by specific legislative enactments. This would seem always to be the case when the beneficiaries were already in existence when the exemption was created and did nothing of a more positive nature to qualify for it than to continue in existence. 6 Yet the cases are not always easy to explain in relation to each other, except in light of the fact that the Court's point of view has altered from time to time. 7