Almost everyone knows that inter vivos trusts can be made revocable or irrevocable.' And the reference to "inter vivos" as opposed to "testamentary" trusts is intentional. Testamentary trusts become effective only upon the death of the settlor by establishing a valid trust in his or her will and, as a result, are by definition irrevocable upon creation (the testator cannot die again nor can he or she undo his or her death to somehow later repudiate the creation of the trust). Hence, it is more precise to say that inter vivos and testamentary trusts may be made irrevocable, but only inter vivos trusts may be made revocable.

Although at one time the default rule in most states was that an inter vivos trust was irrevocable unless the settlor expressly retained the right to later revoke the trust, the modem and current majority view is the opposite: That is, trusts are revocable unless explicitly made irrevocable. Whatever the default rule, it is important to emphasize that inter vivos trusts come in two flavors or varieties: revocable and irrevocable.'

Compare, however, wills that become effective only upon the death of the testator. By definition and in every jurisdiction, wills are ambulatory documents and can always be revoked prior to death.' Indeed, there is no way for a putative testator to make an irrevocable will, meaning that there is no legal method by which an individual can commit to execute a will that is going to be effective upon that individual's death. In a legal regime that has as one of its primary goals the validation of the will maker's freedom of testation or disposition, it is somewhat surprising that individuals have no option to commit their future selves to a will executed by their present self.

Alex M. Johnson Jr., Is It Time for Irrevocable Wills?, 53 University of Louisville Law Review, 393–431 (2016).