No state power is more fearsome than the power to imprison people. Habeas corpus was enshrined in the U.S. Constitution to constrain that power. It is a basic right that allows anyone in American territory to challenge the legality of their detentions before a federal judge. The Constitution limits Congress's power to revoke habeas corpus to periods of rebellion or invasion. The Military Commissions Act eliminated the protection of habeas corpus for detainees at Guantánamo Bay and elsewhere. To eliminate this essential American value makes us more like those we are fighting against. Fortunately, a 5-4 ruling by the U.S. Supreme Court in June 2008 restored habeas corpus rights to those held at Guantánamo. The one-vote majority shows the vulnerability of habeas corpus and other important rights as lawmakers struggle to balance security and civil liberties. The NYCLU is working to defend and restore the due process rights of those detained at Guantanamo and other U.S. government facilities. With the ACLU, it sued the Obama administration in August 2009 for access to a legal memo from the Justice Department Office of Legal Counsel that reportedly addresses the constitutional rights that Guantánamo detainees could legally claim during military commission proceedings in the U.S.