Veterans disabled during military service are entitled to disability benefits. Service-connection presumptions make it easier to prove that exposure to toxins during warfare caused disease or injury, which would be difficult or impossible otherwise. The Agent Orange Act created a presumption that Vietnam veterans who contract certain diseases were exposed to a toxic herbicide. The presumption applies for veterans who served on land or those who served on inland waterways like rivers, known as brown-water veterans. The act does not extend to those who served exclusively in open waters around Vietnam, known as blue-water veterans. The Department of Veterans Affairs (VA) publishes the Adjudication Procedures Manual to guide its employees on which veterans are entitled to the presumption. In 2016, the VA revised the manual to exclude those who served in bays, harbors, and ports from the presumption. The VA did not follow notice-and-comment procedures or publish the changes in the Federal Register or the Code of Federal Regulations. The manual bound only VA-claims processors, not the Board of Veterans’ Appeals. Veteran Robert Gray and Blue Water Navy Vietnam Veterans Association (plaintiffs) sued the VA secretary (defendant), asking the court to invalidate the revisions.