4.1.1. Requirement of Just Compensation.Federal acquisitions entail different appraisal standards than other types of valuation problems because they involve payment of just compensation, and the meaning of just compensation is a question of substantive right “grounded upon the Constitution of the United States.”165 Because only the United States Supreme Court can make binding interpretations of the Constitution,166 questions with respect to just compensation must be resolved under federal common law—that is, case law.167 These questions most frequently arise in federal condemnation cases. As the Supreme Court observed: “Our jurisprudence involving condemnations…is as old as the Republic and, for the most part, involves the straightforward application of per se rules.”168 Those rules form the basis of these Standards. While most of the case law cited in these Standards stems from the federal exercise of eminent domain, just compensation must be paid in many other types of federal acquisitions, whether or not condemnation may be involved.169 

These Standards explain the valuation requirements that apply to all federal acquisitions involving “the measure of compensation…grounded upon the Constitution of the United States.”170 The underlying principles of just compensation remain in force even if special legislation or other considerations may require exceptions to certain aspects of these Standards. Where just compensation is concerned, a reliable process is necessary to ensure a just result,171 “and it is the duty of the state, in the conduct of the inquest by which the compensation is ascertained, to see that it is just, not merely to the individual whose property is taken, but to the public which is to pay for it.”172