Property: Rule Against Perpetuities

The Rule Against Perpetuities (RAP) is the property doctrine designed to prevent land and wealth from being tied up by long-dead owners for generations. It polices “remote” future interests, meaning interests that might not become certain (vest) until too far into the future. Students often find RAP conceptually difficult because it blends technical timing rules, hypothetical scenarios, and the structure of future interests. Practitioners, meanwhile, encounter RAP as a risk-management issue in wills, trusts, and class gifts.

At its core, RAP asks one question: Is it guaranteed that the interest will vest or fail within the allowed time period? If the answer is no, the interest is void from the start.

What the Rule Is Trying to Prevent

Property law generally allows owners to split ownership over time. Someone can have a present possessory estate, while others hold future interests that may take effect later. Without limits, a grantor could attempt to control property indefinitely through contingent future interests that might hang over title for centuries. That uncertainty can chill development, complicate transactions, and undermine the alienability of property.

RAP is the traditional common-law mechanism that limits this dead-hand control by forcing future interests to resolve within a bounded time.

The Classic Common-Law Statement

The classic formulation is:

An interest is void unless it must vest, if at all, no later than 21 years after the death of some life in being at the creation of the interest.

Two points matter:

1. The rule is about vesting, not possession. An interest can vest now and become possessory later without violating RAP.
2. The test is certainty at the moment the interest is created. If there is any possibility the interest might vest too late, it is void immediately.

The measuring period is often summarized as “lives in being plus 21 years.” The “21 years” is historically tied to a generation reaching adulthood and provides a fixed buffer.

Which Interests Are Even Subject to RAP

RAP does not apply to everything. It primarily targets contingent future interests where vesting is uncertain.

Common interests to check:

• Contingent remainders (e.g., “to A for life, then to B if B graduates law school”).
• Executory interests (e.g., “to A, but if alcohol is ever served on the premises, then to B”).
• Certain class gifts where the membership or shares are not fixed.

Interests typically not subject to RAP:

• Present possessory estates.
• Reversions and possibilities of reverter retained by the grantor (at common law).
• Indefeasibly vested remainders.
• Often, vested remainders subject to divestment are treated differently depending on the jurisdiction and the precise contingency, but the safest approach is to analyze the vesting condition carefully rather than rely on labels.

The practical takeaway is simple: whenever you see “if,” “when,” “provided that,” “but if,” or an open-ended condition, RAP should be on your radar.

Measuring Lives: Choosing the Relevant Human Clock

The “life in being” is not any random person. It must be a person who is:

• Alive at the time the interest is created (the “creation” moment depends on the instrument), and
• Relevant to the vesting of the interest.

In a deed, the relevant time is usually when the deed is delivered. In a will, it is generally at the testator’s death. In a trust, it depends on whether the interest is created upon execution or becomes effective later under applicable law, but the key is that RAP measures from the moment the interest becomes legally operative.

A measuring life can be someone mentioned in the instrument (like A, B, or “A’s children”), but it can also be someone not named, as long as that person’s life is connected to when vesting must occur. The goal is to find lives that make vesting timing certain within the permissible period.

Vesting: What Counts as “Vested” for RAP Purposes

For RAP, an interest is vested when the identity of the taker is known and any conditions precedent have been satisfied. Three common sources of uncertainty trigger RAP problems:

1. Uncertain takers

“To A for life, then to A’s first grandchild to become a doctor.” No grandchild may exist yet, and even if one exists, the condition might be satisfied far in the future.

1. Uncertain conditions

“To A, but if the property is ever used for commercial purposes, then to B.” The triggering event could occur centuries later.

1. Class gifts with open membership

“To A for life, then to A’s children who reach 30.” Even if some children exist, another child could be born later, and reaching 30 could be beyond the allowed period.

RAP does not require that the interest actually vests late. It asks whether it might vest late, based on the possibilities allowed by the language.

The “Bad as to One, Bad as to All” Problem in Class Gifts

Class gifts are where RAP becomes especially unforgiving. A class gift is a gift to a group identified by a label, like “children,” “grandchildren,” or “issue.”

Two recurring issues dominate:

The all-or-nothing rule

If there is a possibility that any member of the class might take outside the perpetuities period, the entire class gift may be void at common law. This is why class gifts to “A’s grandchildren who reach 25” can be dangerous: a grandchild could be born after the relevant measuring life dies, and then reach 25 more than 21 years later.

When the class closes

Even when the class gift itself is not void, determining when membership is fixed can be difficult. Doctrines that close classes for distribution purposes (often discussed alongside RAP) matter because they affect whether new members can join and whether the gift can vest in time. In RAP analysis, a gift that stays open too long can create the “possibility” of late vesting.

Practical RAP Analysis: A Structured Way to Think

A reliable approach is:

1. Identify the future interest you are testing and who holds it.
2. Identify the condition precedent to vesting, if any.
3. Pick plausible measuring lives connected to the vesting condition.
4. Ask: Is it certain the condition will be resolved (either satisfied or impossible) within those lives plus 21 years?

If you cannot make vesting certain within the period, the interest is void from the outset, and the conveyance is read as though that interest had never been written.

Reform Approaches: How Modern Law Softens the Common-Law Rule

Because the common-law RAP can invalidate gifts that seem reasonable to ordinary people, many jurisdictions have adopted reforms. Two broad reform approaches are common:

Wait-and-see

Instead of voiding an interest based on mere possibility, a wait-and-see system evaluates what actually happens. If the interest in fact vests within the permitted period, it is valid; if not, it fails. This reduces the “gotcha” character of the common-law rule.

Cy pres (reformation)

Under a cy pres-style approach, a court may reform the language to approximate the grantor’s intent while bringing the disposition into compliance. For example, a gift conditioned on reaching age 30 might be reformed to age 21 if that preserves the general plan and cures the perpetuities problem.

Reform doctrines reflect a policy shift: preserving intent where possible, while still preventing long-term restraints on alienability.

Why the Rule Still Matters

Even where RAP has been modified or narrowed, the underlying concerns remain relevant:

• Title marketability: contingent interests that linger can create uncertainty for buyers and lenders.
• Estate planning: trust terms and age-contingent gifts can unintentionally create perpetuities issues.
• Drafting discipline: RAP forces careful thinking about contingencies, class definitions, and vesting mechanics.

The Rule Against Perpetuities is less about memorizing a slogan and more about learning to read future-interest language with precision. Once you internalize the core idea, that the law demands vesting certainty within a limited human time frame, the doctrine becomes a logical tool rather than a puzzle.