This is an unofficial version of a Massachusetts General Law.
Section 5-504
(a) The death of a principal who has executed a written power of attorney, durable or otherwise, shall not revoke or terminate the agency as to the attorney in fact or other person, who, without actual knowledge of the death of the principal, acts in good faith under the power. Any action so taken, unless otherwise invalid or unenforceable, binds successors in interest of the principal.
(b) The disability or incapacity of a principal who has previously executed a written power of attorney that is not a durable power shall not revoke or terminate the agency as to the attorney in fact or other person, who, without actual knowledge of the disability or incapacity of the principal, acts in good faith under the power. Any action so taken, unless otherwise invalid or unenforceable, binds the principal and his successors in interest.
(c) No revocation by a principal under a written power of attorney, durable or otherwise, shall revoke or terminate the agency as to the attorney in fact or other person who, without actual knowledge of the revocation, acts in good faith under the power or relies in good faith on acts under the power. Any action so taken or relied upon, unless otherwise invalid or unenforceable, binds the principal and successors in interest of the principal. As to a person other than the attorney in fact, such person shall not be deemed to have actual knowledge unless the revocation is in a writing executed by the principal or a duly appointed personal representative of the principal and is actually received by such person or, in the case of transactions involving real estate or any interest therein, is recorded in due course as provided in section 25 of chapter 184.