What is Rule Against Perpetuities?

Legal Definition
The common law rule against perpetuities forbids instruments (contracts, wills, and so forth) from tying up property for too long a time beyond the lives of people living at the time the instrument was written. For instance, willing property to one's great-great-great-great grandchildren (to be held in trust for them, but not fully owned, by the intervening generations) would normally violate the rule against perpetuities. The law is applied differently or not at all, and even contravened, in various jurisdictions and circumstances.

Stated more formally, the common law rule against perpetuities forbids some future interests (traditionally contingent remainders and executory interests) that may not vest within the time permitted; the rule "limits the ability of a decedent to exercise dead hand control over property, which the state wishes to be alienable. In essence, the rule prevents a person from putting qualifications and criteria in his/her will that will continue to control or affect the distribution of assets long after he or she has died, a concept often referred to as control by the "dead hand" or "mortmain".

The rule is often stated as follows: “No interest is good unless it must vest, if at all, not later than twenty-one years after the death of some life in being at the creation of the interest.” For the purposes of the rule, a life is "in being" at conception. Although most discussions and analysis relating to the rule revolve around wills and trusts, the rule applies to any future dispositions of property, including options. When a part of a grant or will violates the rule, only that portion of the grant or devise is removed. All other parts that do not violate the rule are still valid. The perpetuities period under the common law rule is not a fixed term of years. By its terms, the rule limits the period to at the latest 21 years after the death of the last identifiable individual living at the time the interest was created ("life in being"). This "measuring" life (often incorrectly called the "validating" life) need not have been a purchaser or taker in the conveyance or devise. The measuring life could be the grantor, a life tenant, a tenant for a term of years, or in the case of a contingent remainder or executory devise to a class of unascertained individuals, the person capable of producing members of that class. Any one of the "measuring" lives that vindicates the conveyance by resolving all contingencies will be called a "validating" life. This is because this "measuring" life has made the conveyance.

The rule against perpetuities at common law has been amended by various statutes. In England, the Statute of Uses (1536) and the Statute of Wills (1540) and the consequent rise of flexible future interests made the rule a significant judicial tool in defeating the intent of landowners to impose limitations on remote future owners in grants and devises. Major alterations to the common law rule in the United Kingdom came into effect under the Perpetuities and Accumulations Act 1964, including the application of the traditional 21-year limitation period to options.

The rule is notoriously difficult to properly apply, as pointed out by a 1961 decision of the Supreme Court of California which held that it was not legal malpractice for an attorney to draft a will that inadvertently violated the rule against perpetuities. Therefore, in the United States it has been abolished by statute in Alaska, Idaho, New Jersey, Pennsylvania, Kentucky, and South Dakota. The Uniform Statutory Rule Against Perpetuities validates non-vested interests that would otherwise be void as violating the common law rule if that interest actually vests within 90 years of its creation; it has been enacted in 29 states (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Indiana, Kansas, Massachusetts, Minnesota, Montana, Nebraska, Nevada, New Jersey, New Mexico, North Carolina, North Dakota, Oregon, South Carolina, South Dakota, Tennessee, Utah, Virginia, Washington, West Virginia), the District of Columbia, and the U.S. Virgin Islands, and is currently under consideration in New York. Other jurisdictions apply the "wait and see" or "cy-près doctrine" that validates contingent remainders and executory interests that would be void under the traditional rule in certain circumstances. These doctrines have also been codified in the United Kingdom by the 1964 statute.
-- Wikipedia
Legal Definition
A common law property rule that states that no interest in land 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. Because the meaning of this rule is virtually impossible to decipher, many states have modified it, and some have abolished it altogether.
Legal Definition
An older legal ruling that states that abenficiary must have the property left to him, transferred to him within a period of 21 years.
Legal Definition
“No interest subject to a condition precedent is good, unless the condition must be fulfilled, if at all, within twenty-one years after some life in being at the creation of the interest.” See 49 Am. St. Rep. llfi, note, quoting Gray on Perpetuities.
-- Ballentine's Law Dictionary