The Rule Against Perpetuities is the doctrine 1Ls fear most, and for good reason: it's counterintuitive, it punishes drafters for scenarios that will never actually happen, and professors love it precisely because it separates students who memorized rules from students who can apply them under pressure. Here's the good news—RAP is not as mysterious as it looks. It is a mechanical rule with a fixed set of traps, and once you learn the traps you can spot a RAP problem in seconds. This page gives you the rule, the elements, the step-by-step method, and the three exam killers that show up over and over.

What is the Rule Against Perpetuities?

The Rule Against Perpetuities provides that no interest in property is valid 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. That single sentence—usually attributed to Professor John Chipman Gray—is the entire common-law rule, and it is worth memorizing verbatim because professors quote it and expect you to unpack it.

The purpose is policy: the law does not want dead hands controlling property forever. If a grantor could tie up land or a trust with conditions that might not resolve for centuries, property would be locked out of the market and future generations would be bound by the whims of long-dead owners. RAP forces every contingent interest to resolve—either vest or fail—within roughly a generation plus 21 years. If an interest might stay contingent longer than that, the law voids it at the moment of creation.

The Rule Broken Into Elements

Read the rule slowly, because every word is doing work:

1. "No interest is valid" — RAP applies only to certain future interests. Identify the interest first (this is where most students go wrong).
2. "unless it must vest, if at all" — The interest must either vest or fail definitively. "Must" means certainty—if there is any possibility it stays open too long, it fails.
3. "no later than 21 years" — The perpetuities period is a fixed 21 years...
4. "after the death of some life in being" — ...measured from the death of a person alive when the interest was created. This person is the measuring life (also called the validating life).
5. "at the creation of the interest" — For a will, that's the testator's death; for an inter vivos transfer, that's the moment of the grant. This is your fixed vantage point—you judge everything as of this instant.

Which Interests Does RAP Apply To?

This is the threshold question and it's where you earn or lose easy points. RAP applies ONLY to:

• Contingent remainders (remainders subject to a condition precedent or held by an unascertained person).
• Executory interests.
• Vested remainders subject to open (class gifts where the class can still grow).
• Options to purchase and rights of first refusal (in most jurisdictions, when not tied to a current leasehold).

RAP does NOT apply to:

• Any interest held by the grantor—reversions, possibilities of reverter, and rights of entry are all RAP-exempt.
• Vested remainders (not subject to open) and other already-vested interests.
• Present possessory estates.

Mnemonic worth keeping: RAP hunts contingent and class interests in third parties. If the grantor holds it, or it's already vested, RAP goes home hungry.

The Step-by-Step Method for Attacking Any RAP Problem

Do these five steps in order, every time. Skipping the classification step is the single most common exam error.

1. Classify the interest. Is it a contingent remainder, executory interest, or vested remainder subject to open? If it's a grantor's interest or already vested, RAP does not apply—stop and say so. You get points for correctly excluding an interest.
2. Fix the creation date. Will = testator's death; deed = date of conveyance. Everything is judged as of this moment.
3. Identify the condition that must be satisfied for the interest to vest. What has to happen? "When A's first child reaches 25." "If the land is ever used for non-residential purposes."
4. Find a validating (measuring) life. Ask: is there a person alive at creation such that we will KNOW, within 21 years of that person's death, whether the interest vests or fails? If yes, the interest is GOOD. If you cannot find such a person for any interest, it is VOID.
5. Apply the 'what might happen' test. If there is ANY possible chain of events—however absurd—in which the interest could vest more than 21 years after every life in being has died, the interest fails. This is where the fertile octogenarian and friends live.

Key mindset: common-law RAP is a rule of logical possibility, not probability. You are not asking what will happen. You are asking whether there is any conceivable universe in which it vests too late. If yes, void—today, at creation, before anything actually happens.

Worked Example 1: A Good Gift

"To A for life, then to A's first child to reach 21." Suppose A has no children yet. Is the remainder valid?

Classify: contingent remainder (the taker—A's first child to reach 21—is unascertained). RAP applies. Condition: some child of A must reach 21. Measuring life: A. Any child of A must be born within A's lifetime (or within a gestation period after A's death) and must reach 21 within 21 years of A's death. So we will know whether the interest vests or fails within 21 years (plus gestation) of A's death. Valid. A is the validating life.

Worked Example 2: A Void Gift (Age Contingency Too High)

"To A for life, then to A's first child to reach 25." Same facts, A has no children.

Now change 21 to 25. Imagine A has a child, then A dies when that child is 2 years old, and that child is A's only child. We must wait 23 more years to know if the interest vests—more than 21 years after A's death. And there is no other measuring life (a child born after creation is not a life in being). Because there is a possible scenario in which vesting occurs more than 21 years after all lives in being are dead, the interest is VOID. This is the classic "age beyond 21" trap.

The Three Classic Exam Killers

These are the fact patterns professors recycle. Learn them cold—if you can name and explain all three, you can handle most RAP hypos.

1. The Fertile Octogenarian

The common law conclusively presumes that any living person, regardless of age or medical reality, can have more children. So an 80-year-old woman (or a 5-year-old) is treated as capable of producing new offspring who would not be lives in being at creation. This presumption creates remote-vesting possibilities that void gifts to grandchildren and other multi-generational class gifts. Example: "To A for life, then to A's children for their lives, then to A's grandchildren." Even if A is 90, the law assumes A can have a new child (not a life in being) who then produces a grandchild decades later—voiding the grandchildren's interest.

2. The Unborn Widow

"To A for life, then to A's widow for life, then to A's surviving children." The trap: A's "widow" is whoever A is married to at death—she might not be alive now, and might be someone born after the grant. Because the widow may not be a life in being, and the children's interest vests only at the widow's death, that death could occur more than 21 years after every current life in being is gone. The children's remainder is void.

3. The Slothful Executor

"To my grandchildren who are living when my estate is probated." Probate could theoretically drag on for more than 21 years after all lives in being die. Because vesting is tied to an administrative event with no built-in time limit, the gift can fail. Courts treat the possibility of delayed probate as enough to void the interest under strict common-law RAP.

The Exam Trap That Sinks Students

The number-one mistake is failing to classify the interest before applying RAP. Students see a future interest, panic, and run the RAP analysis on a reversion or a vested remainder—interests RAP never touches. Always classify first. The second most common error is analyzing what actually happens rather than what might happen; RAP at common law is a rule of possibilities frozen at the moment of creation. The third is forgetting the class-gift 'all-or-nothing' rule: if a class gift is void as to any potential member, it is void as to the entire class (subject to the sub-class and Rule of Convenience exceptions your casebook may cover).

Modern Reforms: Wait-and-See and USRAP

Because strict common-law RAP voids gifts that would almost certainly have been fine, most states have softened it. Know these on your exam if your professor covers them:

• Wait-and-see (second-look) doctrine: Instead of voiding an interest based on hypothetical possibilities at creation, courts wait to see what actually happens during the perpetuities period and only void the interest if it in fact fails to vest in time.
• Uniform Statutory Rule Against Perpetuities (USRAP): Adopted in many states, it provides an alternative 90-year vesting period. An interest is valid if it satisfies either the common-law rule OR actually vests within 90 years of creation.
• Cy pres / reformation: Some statutes let courts reform an offending grant to carry out the grantor's intent while complying with RAP (e.g., reducing an age contingency from 25 to 21).
• Abolition: A growing number of states have abolished RAP entirely for trusts, enabling perpetual 'dynasty trusts.'

Exam tip: most professors still test the strict common-law rule because it teaches the analytical discipline. If a reform doctrine is on the syllabus, the answer structure is usually: run common-law RAP first, conclude the interest is void, then note that under wait-and-see or USRAP the interest would likely be saved.

Related Doctrines and How They Interact

• The Rule Against Restraints on Alienation shares RAP's policy (keeping property marketable) but is a separate doctrine—don't conflate them. RAP polices remoteness of vesting; restraints on alienation police direct limits on transferability.
• Future interests classification (contingent vs. vested remainders, executory interests) is the prerequisite skill—if you can't classify, you can't run RAP.
• Class gifts and the Rule of Convenience, which closes a class when a member becomes entitled to possession, can rescue some gifts from the all-or-nothing RAP problem.
• The doctrine of merger and the destructibility of contingent remainders, where still recognized, can eliminate contingent interests before RAP even matters.

The One-Paragraph Answer You Can Reproduce Under Pressure

When a RAP issue appears, write it like this: "The interest at issue is a [classify]. RAP applies to such interests. The interest is created at [date]. For the interest to vest, [condition] must occur. To satisfy RAP, there must be a life in being at creation by whose death-plus-21-years we will know whether the interest vests or fails. Here, [either identify the validating life and conclude valid, OR describe the possible remote-vesting scenario and conclude void]. [If applicable: Under a wait-and-see or USRAP jurisdiction, the interest would be saved because...]." That template earns points on virtually any RAP question.