Rule Against Perpetuities

The Rule Against Perpetuities (RAP) is one of the most notoriously difficult doctrines in property law. In its classic formulation, the rule provides: "No interest is good unless it must vest, if at all, not later than twenty-one years after some life in being at the creation of the interest."

The rule operates as a limit on the dead hand — the ability of grantors to control the use and disposition of property long after their death. By requiring future interests to vest within a reasonable time period, the RAP ensures that property remains freely alienable and is not tied up in perpetual restrictions.

The rule applies to contingent remainders, executory interests, and certain vested remainders subject to open (class gifts). It does not apply to present interests, vested remainders, or future interests retained by the grantor (reversions, possibilities of reverter, rights of entry).

The classic analysis requires identifying the measuring life — a person alive at the creation of the interest whose life serves as the timing benchmark. The interest must vest (or be certain to fail) within 21 years of the measuring life's death. If there is any possibility, however remote, that the interest might vest beyond this period, the interest violates the rule and is void from the beginning.

The rule is applied using the "what might happen" test rather than the "what actually happened" test. This means that an interest is evaluated based on hypothetical scenarios at the time of the grant, not based on actual events. The "fertile octogenarian" and "unborn widow" are famous hypothetical scenarios used to demonstrate that interests can violate the rule even when common sense suggests they will vest in time.

Many jurisdictions have reformed the RAP through wait-and-see statutes (which evaluate validity based on actual events), the Uniform Statutory Rule Against Perpetuities (which provides a 90-year alternative period), or outright abolition. Understanding the traditional rule remains important, however, because it is the foundation for all reform approaches.

On property exams, RAP problems require meticulous analysis: classify the interest, identify possible measuring lives, and test whether the interest must vest within the period. Practice is essential — RAP is a skill-based doctrine that rewards methodical analysis.