This guide covers human subjects research law for research counsel, institutional officials, sponsors, sites, and IRB professionals. Part 1 sets out the ethical foundations and the statutory architecture, and Part 2 resolves the applicability question that determines everything downstream. Part 3 covers IRB composition, review levels, and approval criteria, while Part 4 treats informed consent element by element, including the exculpatory language prohibition and the waiver standards. Part 5 addresses vulnerable populations and the additional protections in each subpart, and Part 6 covers the FDA product pathways, registration, and financial disclosure. Part 7 addresses privacy, HIPAA authorization, and secondary use, and Part 8 covers the clinical trial agreement provisions that carry the money and the risk. Parts 9 through 14 address reporting obligations, inspections and enforcement, civil liability, decentralized and emerging models, practice guidance by role, and a worked example.