*i If a citizen thinks that an obligation of this kind is impaired by a law passed in his State, he may refuse to obey it, and may appeal to the Federal courts.

*j [Footnote i: It is perfectly clear, says Mr.Story ("Commentaries," p.
503, or in the large edition Section 1379), that any law which enlarges, abridges, or in any manner changes the intention of the parties, resulting from the stipulations in the contract, necessarily impairs it.
He gives in the same place a very long and careful definition of what is understood by a contract in Federal jurisprudence.

A grant made by the State to a private individual, and accepted by him, is a contract, and cannot be revoked by any future law.

A charter granted by the State to a company is a contract, and equally binding to the State as to the grantee.

The clause of the Constitution here referred to insures, therefore, the existence of a great part of acquired rights, but not of all.