Courts and Congress are often reluctant to constrain the executive branch when it limits individual rights in the pursuit of national security. Many scholars have argued that mechanisms within the executive branch can supply an alternative constraint on executive power—whether as a preferred alternative due to the comparative advantages of such institutions or as a second-best option necessitated by congressional and judicial abdication. Despite this interest in the “internal separation of powers,” there is very little attention to what such internal mechanisms are actually doing to protect individual rights.

I argue that Inspectors General (IGs), little-noticed oversight institutions within federal agencies, are now playing a significant role in monitoring national security practices curtailing individual rights. IGs have investigated the post-9/11 detentions of immigrants, the use of National Security Letters (NSLs) to obtain personal records, coercive interrogations of terrorist suspects, extraordinary rendition, military monitoring of political protests, and many other controversial counterterrorism practices. Analyzing five IG reviews at the Departments of Justice, Homeland Security, and Defense, and the Central Intelligence Agency, I argue that these investigations varied significantly in independence and rigor. At their strongest, IG reviews provided remarkable transparency on national security practices, identified violations of the law that had escaped judicial review, and even challenged government conduct where existing law was ambiguous or undeveloped. Such reviews protected rights where courts had failed and significantly reinforced other forms of oversight. At the same time, even stronger reviews largely did not result in remedies for most victims, repercussions for high-level executive officials, or significant rights-protective constraints on agency discretion. These case studies illuminate the potential strengths and limitations of IG rights oversight: IGs are well suited to increase transparency, evaluate the propriety of national security conduct, and reform internal procedures; on the other hand, their independence can be undermined, they may avoid constitutional questions, and they rely on political actors to implement reforms. IGs can help protect individual rights against national security abuses and should be modestly strengthened, but they do not displace the need for robust external oversight of the national security executive.