You’ve probably heard of it. You probably even know it’s Latin. But do you really know what habeas corpus means?

The “Great Writ” of habeas corpus is a fundamental right in the Constitution that protects against unlawful and indefinite imprisonment. Translated from Latin it means “show me the body.” It has historically been an important instrument to safeguard individual freedom against arbitrary executive power.

Habeas corpus isn’t a fancy legal term, it’s the freedom from being thrown in prison illegally, with no help, no end in sight and with no due process. No president should ever be given the sole power to call someone an enemy, wave his hand, and lock them away indefinitely. The Founders made the president subject to the rule of law. They rejected dungeons and torture, and instead chose due process and fairness.

The concept of habeas corpus is a centuries-old legal procedure that is even older than the United States. The first recorded use of the phrase habeas corpus dates back to 1305, to the reign of England’s King Edward I.

So when the 109th Congress passed and the President signed the Military Commissions Act of 2006 and, in a specific context, effectively abolished the writ of habeas corpus for certain people, they were turning away from a centuries-old tradition that is a cornerstone of our Constitution, and our freedom.

Want to learn more about this history of habeas corpus? Check out the interactive timeline created by the ACLU.