When a testator signs his last will and testament and he has it witnessed and notarized, it becomes a legally binding document. The only person who can amend it or revoke it is the testator himself. As long as his will meets the legal requirements in his state, the court will uphold it. No one -- not even his spouse -- can unilaterally change its terms, but she can override her own bequest in some states.
Most state codes include provisions for elective or statutory shares in the event a testator omits his spouse from his will, or if he bequeaths her only a small share of his estate. The dissatisfied spouse can notify the court that she would like to reject the terms of the will; the court will then allow her to take a statutory percentage of the estate instead. Statutory means that state law defines the exact percentage. It varies from jurisdiction to jurisdiction, but is commonly about one-third of the decedent's assets. When a dissatisfied spouse does this, it legally changes her spouse’s will in the respect that his beneficiaries only receive the remaining balance after her statutory percentage; they will not receive all that the testator intended to give them. However, it does not change any other terms of the will.
Community Property States
Community property states do not generally recognize elective shares. In these states, spouses equally own all marital property by law. A surviving spouse automatically retains her half of the marital property when the other spouse dies; he only has a right to bequeath his own half. If one spouse tries to leave more than his half of community property to beneficiaries in his will, the surviving spouse can notify the court and block the bequest. This, too, would change his will, but only those bequests in which he attempted to give property that did not legally belong to him.
Joint and Mutual Wills
Some spouses elect to leave joint or mutual wills. A joint will is co-signed by both spouses and leaves everything they own to each other. When one spouse dies, the other inherits. Other heirs generally do not receive their bequests until the second spouse dies, when the property passes on. Mutual wills follow the same premise as joint wills, but involve two wills and a separate written agreement that neither spouse will change their own. As long as both spouses are living, they can change their mutual will by consent, but when one of them dies, it becomes irrevocable. This agreement prevents one spouse from changing her will after the other spouse dies. Before that time, she can change it any time she likes, but she has no control over her spouse’s mutual will.
A power of attorney gives someone else, the agent, the right to make personal transactions and decisions on behalf of the grantor. Many people believe that when their spouse gives them power of attorney, they can use this document to change the terms of his will. This is not true. A power of attorney does not authorize a spouse or anyone else named as the agent to write a will for the individual granting it, or to change the terms of his existing will.