Few provisions of the American Constitution have had such a tumultuous history as the contract clause. Prompted by efforts in a number of states to interfere with debtor-creditor relationships after the Revolution, the clause--Article I, Section 10--reads that no state shall "pass any. . . Law impairing the Obligation of Contracts." Honoring contractual commitments, in the framers' view, would serve the public interest to encourage commerce and economic...