Entering the White House in 2009, President Barack Obama committed to closing the military detention facility at Guantanamo Bay in Cuba. Eight years later, the facility remains open. This Article uses the puzzle of why Obama’s goal proved so recalcitrant as a case study of separation‐of‐powers constraints upon presidential power. Deploying a combination of empirical, doctrinal, and positive political science tools, it isolates the salient actors and dynamics that impeded Obama’s goal. Its core descriptive finding is that a bureaucratic–legislative alliance was pivotal in blocking the White House’s agenda. This alliance leveraged its asymmetrical access to information to generate constraints on the President. The most significant of these constraints operated through political channels; statutory prohibitions with the force of law were of distinctly secondary importance. The analysis, furthermore, sheds light on why individualized judicial review, secured through the mechanism of habeas petitions under the Constitution’s Suspension Clause, had scant effect. Contrary to standard approaches to the Constitution’s separation of powers, the case study developed here points to the value of granular, retail analysis that accounts for internally heterogeneous incentives and agendas instead of abstract theory that reifies branches as unitary and ahistorical entities.