Salim Ahmed Hamdan never planted a bomb, never took a hostage, never wielded a box cutter, never fired a weapon in anger, and never planned an attack of any kind.

What he is alleged to have done, according to his US military commission charge sheet, is work as Osama bin Laden's driver in Afghanistan.

So how could military prosecutors at Guantánamo Bay, Cuba, charge him with being a terrorist and war criminal? The answer boils down to a single word: conspiracy.

The same legal approach that helped put mafia dons, capos, and associates behind bars in America is at the center of US military efforts to prosecute suspected Al Qaeda members for war crimes.

But now in the wake of the US Supreme Court's decision in the Hamdan case invalidating the military commission process, it is unclear to what extent military prosecutors can continue to use conspiracy as a war crimes charge.

The Bush administration is asking Congress to simply pass a law recognizing conspiracy as a war crime.

But some legal experts warn that the law of war is a reflection of both domestic and international standards that should not be watered down unilaterally by US lawmakers. They say such a move would further undermine US standing as a champion of human rights and set the stage for another major defeat in the courts for President Bush.

"This is just contempt for the court's opinion," says George Fletcher, a professor at Columbia Law School who authored a friend of the court brief in the Hamdan case that first raised the conspiracy issue. "If Congress says we can go around it, that is just crazy. They don't understand what they are doing."

In its June opinion, a five-member majority of justices struck down the military commissions at Guantánamo because they did not comply with the requirements of the Uniform Code of Military Justice and Common Article 3 of the Geneva Conventions. That part of the decision addressed what the high court viewed as fatal procedural defects – including a rule allowing the exclusion of a defendant from parts of his own trial.

Congress is now considering how best to rewrite those procedures to strike the proper balance between a fair trial and safeguarding national security.

But there is another part to the Hamdan decision. Four of the eight justices participating in the case ruled that the military commissions at Guantánamo did not have jurisdiction under the law of war to prosecute suspected Al Qaeda members for allegedly engaging in a conspiracy.

Conspiracy is not a war crime, said Justice John Paul Stevens in his plurality decision. And special military commissions can only try war crimes, he said.

Conspiracy charges for 10

The ruling is significant because all 10 detainees at Guantánamo slated for military commission trials have been charged with conspiracy, and seven of them (including Mr. Hamdan) face only a single conspiracy charge.

According to the Stevens plurality, military prosecutors must base their cases on actual war atrocities or attempted atrocities, not merely on a criminal agreement (conspiracy) to violate war crimes. Legal experts say this significantly increases the burden military prosecutors would face to win convictions at trial, and some say it could make it impossible to convict defendants like Hamdan.

Justice Anthony Kennedy provided the decisive fifth vote striking down Guantánamo commission procedures in the Hamdan decision. But he declined to provide a fifth vote on the jurisdictional question involving conspiracy. Instead, he left the matter to the legislative branch.

"In light of the conclusion that the military commissions at issue are unauthorized, Congress may choose to provide further guidance in this area," Justice Kennedy wrote in his concurrence. "Congress, not the court, is the branch in the better position to undertake the sensitive task of establishing a principle not inconsistent with the national interest or international justice."

Analysts say it is unclear how Kennedy might vote in a future case.

"What does Kennedy think about this? We'll be asking that a lot," says Diane Amann, a law of war expert at the University of California, Davis, School of Law. But she adds, "The fact that Kennedy held back – if I were the government I would not take comfort in that fact."

In a dissenting opinion in the Hamdan case, Justices Clarence Thomas, Antonin Scalia, and Samuel Alito said the law of war is flexible enough to permit military commissions to hear conspiracy cases.

"The plurality's inflexible approach has dangerous implications for the Executive's ability to discharge his duties as Commander in Chief in future cases," Justice Thomas wrote.

The Bush administration agrees with Thomas's expansive view of presidential power. "We believe that the dissenting opinion in Hamdan was correct in its analysis and that the plurality's view on this particular question is not sustainable," Acting Assistant Attorney General Steven Bradbury told a Senate Judiciary Committee hearing on Aug. 2.

In the same hearing, Sen. Dianne Feinstein (D) of California asked the top legal officials for each of the four armed services whether Congress should designate conspiracy as a war crime for use in military commission trials at Guantánamo. Three said yes, one said he would prefer a charge of providing material support to terrorists.

"If the Congress is just going to try to add conspiracy onto the existing military commissions, that could be problematic," says Michael Scharf, director of the Frederick K. Cox International Law Center at Case Western Reserve University School of Law. "I think they are better off leaving conspiracy out of it."

Professor Scharf and other international law experts say that while conspiracy charges are an accepted part of the legal system in the United States and Britain, that legal approach has been rejected by most other countries – including international war-crimes tribunals.

Full rights for mafia, not detainees

In addition, analysts say that when federal prosecutors used conspiracy charges to help convict organized crime figures in the US, the alleged mafia members were afforded all the legal protections of the US court system. In contrast, military commissions don't provide the same range of trial protections.

One alternative to conspiracy, analysts say, is to charge suspects with a form of aiding and abetting. That would bring the military commission process within international standards. But it would also make it harder for prosecutors.

"From a prosecutorial standpoint, prosecuting someone for aiding and abetting requires a heck of a lot more proof than prosecuting them for conspiracy," says Professor Amann. Military prosecutors may not have enough evidence to win an aiding and abetting case, she says.

Scharf says military prosecutors still might win convictions. "My hunch is that everybody they are interested in trying, they can get for either committing the crime [a specific atrocity] or aiding and abetting. They don't really need the conspiracy," he says.

The bottom line, these analysts say, is that conspiracy charges would make it much easier to win convictions, but in the eyes of most of the world such trials would be viewed with suspicion and distrust rather than as beacons of international justice.

"Most people around the world look at the Hamdan decision as a return to the rule of law," Professor Fletcher says. "If Congress defies the Supreme Court and says: 'No, we think we can get around this,' it will hurt the country enormously."