The Supreme Court is poised to consider the most important constitutional controversy that has arisen in the aftermath of the September 11 terrorist attacks: Can a U.S. citizen be deprived of all access to a lawyer and family and imprisoned for as long as a president insists? Can the president, in effect, override the ancient writ of habeas corpus?

Today, April 28, the Court will hear the appeal of Yaser Hamdi, a U.S. citizen who is being held in a military brig in Charleston, South Carolina. For almost two years, Hamdi has been held incommunicado — no contact with visitors, including his lawyer. The Bush administration has maintained that legal counsel is unnecessary because Hamdi has not been charged with a crime; he is instead being held as an “enemy combatant.”

On the surface, the Hamdi case appears to be a no-brainer. Hamdi was apparently one of the Taliban fighters captured in a combat zone in Afghanistan. And his claim of U.S. citizenship is about as thin as it gets — his parents were Saudi citizens who happened to be in the United States on a temporary work visa at the time of Hamdi’s birth. Furthermore, the U.S. military has always captured and held enemy fighters in all of our previous wars. Thus, Hamdi’s legal appeal seems to be devoid of merit.

A close examination of the Hamdi case, however, shows that the constitutional stakes could not be higher. That’s because the Bush administration has been using the Hamdi case to advance a sweeping theory of executive branch power. According to this theory, the president can deprive anyone in the world of his liberty and hold that person incommunicado indefinitely. The president need only be careful to issue an “enemy combatant” order to his secretary of defense, not the attorney general. The president’s legal advisers have made it clear that it does not matter if the prisoner is seized on a battlefield overseas or in some sleepy town in the American heartland. And it does not matter if the prisoner is a foreign national or an American citizen. It is because the courts are being asked to approve this broad claim of executive power that Hamdi’s case is considered pivotal. This is not just about the imprisonment of one man.

To fully understand the implications of the administration’s “enemy combatant” theory, one must first consider the constitutional procedure of habeas corpus. The Constitution provides that “The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it.” The writ of habeas corpus is a venerable legal procedure that allows a prisoner to get a hearing before an impartial judge. If the jailor is able to supply a valid legal basis for the arrest and imprisonment, the prisoner will simply be returned to his prison cell. But if the judge discovers that the imprisonment is illegal, he has the power to set the prisoner free. For that reason, Joseph Story once described the habeas writ as a “great security” for individual liberty.

Speed up to today: Hamdi’s father filed a petition on his son’s behalf. The Bush administration responded to that petition by urging the district court to summarily dismiss the petition because the courts may not “second-guess” the president’s “enemy combatant” determination. That assertion strikes at the heart of habeas corpus. If the judiciary could not “second-guess” the executive’s initial decision to imprison a citizen, the writ never would have acquired its longstanding reputation in the law as the “Great Writ.”

Once the Justice Department admits, as it must, that the writ of habeas corpus has not been suspended, the law is clear. Habeas proceedings are habeas proceedings. And that means the prisoner has to be able to meet with his attorney to adequately prepare for their “day in court,” where they will have an opportunity to persuade a judge that a mistake or abuse has occurred. It is outlandish to suggest that habeas petitions can be filed, so long as the courts throw the petitions out.

The lower court dismissed Hamdi’s habeas petition too casually simply because Hamdi himself has not been heard from. Thus, the Supreme Court should remand the case to the district court for further proceedings. On remand, Hamdi must be allowed to consult with his attorney in private. An evidentiary hearing should then be held and the prisoner should have an opportunity to address the Court and his counsel must have an opportunity to rebut the government’s allegations at the hearing. The government must also be given an opportunity to defend the legality of its actions. If it can persuade an Article III judge that this detention is lawful and proper, Hamdi should be returned to the military brig.

The al Qaeda terrorist network is an evil organization that must be vanquished. But as we go about that task, we must not lose sight of what we are defending. Free societies do not “just happen.” Freedom in America rests upon a framework of checks and balances that was designed by men who were steeped in history and political philosophy. If that framework is neglected, constitutional guarantees will become nothing more than hollow promises on pieces of paper.