This guide covers behavioral health and substance use treatment confidentiality from the threshold coverage question through consent, disclosure, enforcement, and program compliance. It begins with why Part 2 is structured as a prohibition rather than a permission and what follows from that design, then works through the three questions that determine coverage: whether information is patient identifying, whether the holder is a Part 2 program, and whether federal assistance exists. It sets out every element a Part 2 consent must contain and how it differs from an ordinary authorization, the redisclosure prohibition and the notice that must accompany every disclosure, and the exceptions — medical emergency, qualified service organizations, research and audit, crimes on premises, and mandatory reporting — with their documented limits. It treats the court order procedure in detail, including the good cause findings and the heightened showing for investigative purposes. Separate parts address opioid treatment program regulation, parity in coverage, disability and fair housing protections, privilege and duty to warn, civil commitment, program and recovery residence licensure, patient brokering enforcement, and the segmentation problem.