The alleged former driver and bodyguard for Osama bin Laden is at the heart of a US Supreme Court case this week that could determine whether President George W. Bush has the power to use military tribunals in his war on terrorism.
The case, focusing on the war crimes tribunals for prisoners at the US military base in Guantanamo, Cuba, will also weigh the balance of power between the presidency and the courts.
In 90 minutes of arguments tomorrow, the session could produce the most significant ruling on presidential war powers since the end of World War Two.
"Reduced to its essence, the government's argument is that the federal judiciary has no real power to review actions taken by the president in the name of fighting terrorism," wrote University law professor Neal Katyal, who is defending bin Laden's former driver-bodyguard, Salim Ahmed Hamdan.
In revisiting Bush's policies in the war on terrorism for the first time in nearly two years, the Supreme Court will take up a second important issue on whether Guantanamo prisoners can go to court in the United States to enforce the protections of the Geneva Convention.
The Bush administration says the president has the power to create the military tribunals and the protections of the Geneva Convention do not apply. In the past, the Supreme Court has provided a check on the president's powers in the war on terrorism.
Before the justices can rule on either issue, they must decide a third crucial issue - whether a recent law stripped the court of its jurisdiction over the appeal by a Yemeni accused of being Osama bin Laden's bodyguard and driver.
The Detainee Treatment Act, signed by Bush on December 30th, 2005, severely restricts the ability of prisoners at Guantanamo to bring challenges in federal court.
The Bush administration argued the law applied to all existing cases and that the Supreme Court must dismiss Mr Hamdan's appeal without deciding the key issues.
Mr Hamdan's attorneys disagreed. They said the US Congress did not intend to strip the court of the power to decide challenges to the lawfulness of the tribunals.
Over the weekend Newsweek magazine reported that Justice Antonin Scalia in a private meeting in Switzerland dismissed the idea that Guantanamo detainees have constitutional rights. Critics complained that he was prejudging the issue and should step aside, although there was no indication he would.
Formally called military commissions, the special tribunals were authorized by Bush after the September 11th attacks and have been criticized by human rights groups as being fundamentally unfair.