Wong Yang Sung (plaintiff), a Chinese national, was arrested for unlawfully being in the United States. The Immigration and Nationalization Service (INS) (defendant) held a hearing, and the immigration inspector recommended that Wong be deported. The INS approved the recommendation. The Board of Immigration Appeals affirmed. Wong filed a petition for a writ of habeas corpus in the United States District Court for the District of Columbia. Wong argued that his hearing did not comply with the requirements of the Administrative Procedure Act (APA). The INS admitted that the hearing did not comply with the APA but argued that INS hearings did not have to comply with the APA because the statute authorizing deportation did not require a hearing or adjudication. The United States Supreme Court granted certiorari.