Transfer of title must eventually occur, otherwise the property was never willed to another because the willing of the property is perpetually incomplete.
One can place conditions on the transfer of title, but those conditions cannot last forever. They can last quite long, but there is a rule against perpetuities, especially created due to clauses constraining the transfer of of title in wills.
This rule applies to a person who is transferring title, with a conditional clause that bars the full use of the property. If such a clause is limited, then it does not exist in perpetuity. The rule specifically addressed the will's call to reassign title if the transfer's clauses were violated. The maximum limitation historically was the lifetime of some person alive when the will was executed, plus 21 years, to permit an unborn grandchild to inherit.
The reason this rule came about was due to the will of Henry Frederick Howard, the Earl of Arundel and Surrey. It effectively left the dead Earl managing his estates after his death, shifting properties that were bequeathed, based on the possibility of a "more suitable" heir being born after the Earl's death. This will eventually created the most complicated bit of common law that exists to date.
In my totally amatuer attempt to summarize it; it is a combination of at least two ideas:
- a "dead hand" (deceased person) cannot guide the activities of the living forever
- transfer of property (title) must eventually be fully transferred
Exceptions to the rule exist for conditional transfer of title back to the person who originally owned the property, but these exceptions cannot apply when the transfer is to a third party.
This clause in Evan's will,
"If the state violates this clause, the property is to return to the
heirs of the estate of Evan Carroll."
would only be enforceable for a limited amount of time. First, the Estate of a dead Evan Carroll is not a lasting entity, eventually his estate would be closed. Finally, the transfer to the "heirs" of Evan Carroll would be a transfer to a third party, subject to the rule.
Some states interpret their protections against the rule in different ways; but, nearly all states that have revoked the rule have done so by making a new rule (often with easier to manage time limits). A handful claim to have revoked the rule; but, they use other legal approaches to prevent this problem from occurring.
Texas has extended the rule to 300 years while New South Wales, puts the limit at 80 years. Texas's extension seemed to be primarily to permit trust funds to operate legally long after the person establishing it had died.
Consider what happens if such a rule doesn't exist. The title of the property could never be fully transferred, because the clause could never be proven to not have been violated. This would dramatically devalue the property, and clog the courts with suits claiming property held by one family for 100 years isn't theirs because of some evidence just uncovered about what happened 60 years ago. It also would massively complicate the selling of the property, because a clean title could never be proven.
Note that this rule would have no bearing on a covenants not tied to the property's transfer of title.
This rule even made it into a recent Disney case, which is explained far better than I can by the Legal Eagle, Devin James Stone