This article explores how various sources of authority interact to govern psychologists' parenting plan evaluations (child custody evaluations), and remedies that are available when an evaluation is poorly conducted. The law in some jurisdictions may establish specific elements to be included in such evaluations; the professional associations to which psychologists belong may set forth enforceable standards, aspirational guidelines, and white papers; and learned treatises may describe ideal practices. Psychologists may rely on these sources of authority to shape their evaluations, and, finally, may consult with colleagues for guidance.