An Assembly Constitutional Amendment (ACA) refers to a proposed change or addition to the California State Constitution that is introduced and considered through the California State Assembly, one of the houses of the state legislature. This type of amendment requires approval by a two-thirds majority vote in both the Assembly and the State Senate before it can be presented to the voters for final approval through a statewide ballot initiative. The process involves a formal proposal to alter the state’s constitution, often addressing fundamental principles or structures within the government.