A more thorough explanation:

The rule against trusts of perpetual duration is a legal principle that prohibits the creation of trusts that last forever. This rule is also known as the rule against inalienability, which means that property must not be made nontransferable.

For example, if a person creates a trust that is designed to last forever, it would violate the rule against trusts of perpetual duration. The trust must have a specific end date or event that triggers its termination.

Another example is if a person creates a trust that restricts the transfer of the property to future generations. This would also violate the rule against inalienability because it would make the property nontransferable.

The purpose of this rule is to ensure that property remains transferable and can be used for the benefit of society. By limiting the duration of trusts, the law encourages the efficient use of property and prevents it from being tied up in perpetuity.