“So far as may be, the state leaves the rule of right to be declared and constituted by the agreement of those concerned with it. So far as possible, it contents itself with executing the rules which its subjects have made for themselves. And in so doing it acts wisely. For, in the first place, the administration of justice is enabled in this manner to escape in a degree not otherwise attainable the disadvantages inherent in the recognition of rigid principles of law. Such principles we must have; but if they are established pro re nata by the parties themselves, they will possess a measure of adaptability to individual cases which is unattainable by the more general legislation of the state itself.” John Salmond, Jurisprudence 352 (Glanville L. Williams ed., 10th ed. 1947).
pro re nata
pro re nata (proh ree nay-t[schwa]). [Latin “in the light of what has arisen”] Hist. By reason of emergency; arising from exigent circumstances. • The phrase appeared, for example, in reference to a meeting called to address an emergency.