Empirical analysis of the way property rules operate in real cases demonstrates that standards perform core functions in the property law system. Contrary to the intuitive view, rules do not always promote predictability. Because justified expectations are based on both informal and formal sources, predictability will sometimes be improved by framing property doctrines in the form of a standard. While rules seem to make it easier for lawyers to advise clients about property rights, rules may undermine the predictability of property rights if actors in the real world base their expectations on factors other than those legal rules. In such cases, reduction of uncertainty in one area or for one party might increase uncertainty in another area or for another party. Uniform application of rigid rules does not lead to a uniform increase in predictability across the board. Because of the importance of informal expectations for property rights, the conventional wisdom is upside down; when informal expectations diverge from formal rules, standards promote certainty while rules undermine it.
Joseph William Singer, The Rule of Reason in Property Law. UC Davis Law Review, Vol 46, No. 5, June 2013.