José Padilla’s conviction by a federal jury in Miami has already become something of a Rorschach test. Critics of the Bush Administration have argued that the conviction proves that the ordinary criminal justice system works for trying terrorists, and that therefore President Bush did not need to assert the truly extraordinary power of detaining an American citizen arrested on US soil in military custody for more than three years. Meanwhile, Attorney General Alberto Gonzales has hailed the conviction as “a significant victory in our efforts to fight the threat posed by terrorists and their supporters.”

Both sides are wrong. In fact, Padilla’s criminal conviction was a stroke of luck for the Administration. It took a huge gamble in his case, trying him on very weak evidence in the hope of avoiding a Supreme Court test of the President’s asserted power to hold American citizens arrested here as “enemy combatants.” For the moment, the bet has paid off–at least until an appeal overturns it. But do we really want the Administration gambling on our national security?

The gamble began in 2002, when the Administration took Padilla, arrested at Chicago’s O’Hare International Airport, into military custody, denied him access to a lawyer and interrogated him for extended periods of time under circumstances that would render anything they learned from him unusable in a trial against him. It continued the gamble when it “disappeared” high-level Al Qaeda suspects into CIA secret prisons, or “black sites,” where it subjected them to waterboarding and worse in an effort to coerce information from them. There, too, the Administration allegedly gained intelligence about Padilla–but that information will also never be admissible in a court of law because of the brutal way in which it was obtained.

The short-term decisions to gather information in illegal ways made it impossible to bring Padilla to trial on the Administration’s press conference charges that he was pursuing plans to detonate a radiological “dirty bomb,” or, somewhat less dramatically, to explode an apartment building by leaving the gas on and setting it afire. Instead, it was relegated to trying him in Miami as part of a hazy conspiracy that involved no plans to commit any specific terrorist or violent act.

The charges in Miami were that Padilla had attended a terrorist training camp sometime before 9/11. Vast stretches of the three-month trial concerned a conspiracy of two other men to provide support to jihadist fighters in Chechnya and Bosnia. Of 3,000 tape-recorded phone calls introduced into evidence, only two concerned Padilla. The main piece of evidence against Padilla was a “mujahadin data form” that appeared to place him at a terrorist training camp–but prosecutors never offered any evidence that Padilla had used that training to further terrorist activity.

In the end, the prosecution succeeded, as the jury found Padilla guilty of attending the training camp and of one count of conspiracy to maim, murder or kidnap overseas. But given how weak the evidence was, the case could easily have come out the other way–and may not withstand appeal.

If what the Administration says about Padilla is true, this should not have been a close case. But because the Administration obtained its evidence against him through unconstitutional means, it was never able to tell the jury what it really thinks Padilla was up to–planning serious terrorist attacks within the United States, not just training abroad and seeking to support Muslims in Chechnya.

And Padilla is only the tip of the iceberg. There are dozens of people at Guantánamo whom the government accuses of much more serious crimes, including the masterminding of 9/11 itself. Those men may never be tried at all, because of the way the Bush Administration chose to treat them and their fellow suspects.

Our national security should not rest on a wager that we can convict terrorists on weak charges that do not even speak of their most serious crimes. Had it chosen to follow the rule of law at the outset, the Bush Administration could have brought many real terrorists to justice by now. Instead, it is left to declare a major victory when it manages to convict a marginal player for crimes that do not even come close to those the Administration claims he actually committed.