The Access Control Policy is the best choice because it sets out the framework for managing access rights, defining user responsibilities, and specifies how access is granted, reviewed, and terminated. An Acceptable Use Policy typically outlines acceptable behaviors when using company resources but does not specifically address user access management. Data classification policy deals with categorizing organizational data based on its sensitivity and legal requirements but lacks the specifics of user access management. While a change management policy governs how changes to the IT infrastructure are managed to prevent disruptions, it does not directly deal with the assignment and management of access rights.