In probably the most well-known case he handled, Keisler argued on behalf of the government in "Hamdan v. Rumsfeld" in the D.C. Circuit and participated in both the case's appellate and Supreme Court briefs. In addition, he personally led the team that responded to a legal appeal by Sabin Willett, the lawyer for the seventeen remaining Uyghur captives in Guantanamo, that tested the use of a provision of the Detainee Treatment Act in terms of whether or not captives could challenge the rulings of their Combatant Status Review Tribunals.