The U.S. Justice Department defied a court order and refused to produce a key witness Monday in the only criminal trial stemming from the Sept. 11 terrorist attacks to date.

Now, the so-called 20th hijacker, Zacarias Moussaoui, might go free, if U.S. District Judge Leonie Brinkema dismisses the charges as she is expected to do.

It is unacceptable for the prosecutors, backed by Attorney General John Ashcroft, to ignore a federal judge. They argue that the country's national security will be compromised if Moussaoui, who is representing himself, is allowed to question Ramzi bin al-Shibh, one of the accused planners of the attacks.

The chilling worldwide connections in al-Qaida demand new emphasis on protecting sensitive information. And Brinkema has acknowledged that in past rulings.But denying Moussaoui access to bin al-Shibh denies basic constitutional guarantees. Both the government and Moussaoui say bin al-Shibh, currently being held in a secret overseas location, is critical to their case. Brinkema ruled that Moussaoui therefore has a Sixth Amendment right to confront him as a witness.

She also may have support at the appeals level. Chief Judge Wilkins of the Fourth U.S. Circuit Court of Appeals, in a decision to not intervene in the case, warned that his court would not blindly accept all governmental claims of national security.

Brinkema does not have to dismiss the case entirely. She has other options, including throwing out some of the charges, removal of the death penalty as a punishment or allowing the case to continue but informing jurors that the government withheld vital evidence.

She may want to consider a lesser sanction than dismissal. If the case is thrown out entirely, the government has indicated it may seek to put Moussaoui before a military tribunal, where he would have none of the Constitutional trial rights he now enjoys.

The prosecutors said they carry the dual responsibility of prosecuting alleged terrorists and protecting the nation's security. We place a great amount of trust in our government to do both. But we also expect the government to protect the rule of law.