THE UNITED STATES has not conducted trials by military commission since World War II -- and those were hardly a model of fairness. So it's no surprise that the military tribunals that got under way last week at Guantanamo Bay Naval Base in Cuba had some anomalies. The much-delayed tribunals should not be confused with either the lawsuits in federal court brought on behalf of Guantanamo detainees or with the review tribunals the military has belatedly set up to determine if detainees have been properly classified as enemy combatants. They are, rather, criminal courts hearing allegations of war crimes. The trial of accused Sept. 11 conspirator Zacarias Moussaoui has shown the grave difficulties of using federal courts for some Al Qaeda cases, so the commissions represent a critical piece of any realistic strategy for delivering justice in the war on terrorism. But it is crucial that the military process delivers trials that are fair, and appear to be fair to reasonable observers.

The initial signals on this score are mixed. On the positive side, pretrial hearings for four detainees have begun, and the detainees are being given a chance to respond to the serious allegations against them. The members of the commission and its prosecutors and defense teams alike appeared to take their roles and duties seriously. Defense challenges to the service of officers on the five-member commissions yielded candid exchanges. For all the criticism the commissions have taken from human rights groups and others, they did not appear to be kangaroo courts in which the results are preordained.

Still, problems with the process also were on display. The defense lawyers, who are performing a remarkable public service, are seriously understaffed. Translations were spotty and at times inaccurate -- an intolerable problem in a court proceeding in which precise discussion is critical. More fundamentally, the commission's structure and composition are troubling. Some of its members served in Afghanistan while the Guantanamo detainees now on trial were being captured. Its presiding officer is the only lawyer on the panel; this means that he might have grossly disproportionate influence on the commission's rulings. What's more, that presiding officer -- Army Col. Peter E. Brownback III -- is a close friend of the Defense Department official who appoints commission members and will oversee their work. And the department's procedures still lack a provision for appeals to the federal courts, a problem only partly ameliorated by the Supreme Court's recent decision asserting jurisdiction over detentions at the base.

These issues need to be addressed, and they need to be dealt with before the proceedings are so far along that changes would have to be applied retroactively. Once again, Congress is missing in action, leaving essential legislative questions to the executive branch and the courts. This abdication gives the military the ability to run these trials almost any way it sees fit. Officials need to exercise the discipline -- a discipline the Bush administration has rarely shown to date -- of taking the long view and doing the right thing without being forced.