http://en.wikipedia.org/wiki/Habeas_corpusEssentially habeas corpus is the principle by which a government cannot hold prisoners without charge. Basically a prisoner has a right to appear and have charges produced against him/her.
It is quite ancient and a fundamental foundation of Western law. Without it, governments could have the right to arbitrarily imprison people without charges, and in many instances, friends, relatives might not even know the person was seized.
It is not a theoretical issue in 2005, as the Bush administration has essentially suspended habeas corpus in the name of fighting terrorism, reserving the right to themselves to designate someone as a terrorist or supporter of terrorists, seize them and hold them indefinitely without charges.
This does not merely hold for so-called "enemy combatants" in Guantanamo, it has been applied to an American citizen in at least one case, that of Jose Padilla, a U.S. citizen seized on U.S. soil, and imprisoned without charges. The accusations (not charges, there are none) against Padilla were initially that he had plotted to create and detonate a "dirty" radiation bomb in the U.S. These accusations have since mutated to other accusations and the original "dirty bomb" accusations seem to have faded away. There are no formal charges against him, and he is still being held.
I mention this because near the end of the film there is footage of Eisenhower at some dinner or ceremony, speaking about the fact that there is habeas corpus in America, and that ought to provide sufficient legal protection for people accused... We are moving backwards in history and progress.