America's military tribunals through the ages.

With U.S. forces seemingly closing in on Osama Bin Laden, the Bush administration may soon have to decide whether to execute its plan to try suspected terrorists— including American residents —before military tribunals. Just as the Bushies have invoked Abraham Lincoln's suspensions of the privilege of habeas corpus to justify their summary detentions, so they have hearkened back to the use of military tribunals in the Civil War to justify their new proposal. The big difference between the Bush plan (click here for the president's executive order) and Lincoln's plan, of course, is that while Bush intends to try mainly what the Supreme Court has called "enemy belligerents" in his military courts, Lincoln prosecuted American civilians. Still, now as then, using Army courts to try anyone but U.S. soldiers is to court the reproach of posterity.

Lincoln's Army tribunals began operating just a few months after the Civil War began. Disorder was acute in border states such as Maryland and Missouri, which remained loyal to the republic but contained many citizens who sympathized with or aided the Confederate rebels. In Maryland, Lincoln sought to quell the chaos by suspending habeas corpus (as discussed in last week's "History Lesson"). But Missouri was more intractable. In June 1861, the state's governor declared war on the Union forces even as he swore his fidelity to the United States; a month later, all-out combat had consumed the state. Union Gen. John C. Frémont imposed martial law in August.

Martial law, which Army commanders impose on populations when regular governments cease to function, is not the same as military law. According to the Articles of War passed by Congress in 1806, only members of the armed forces can be tried under military law. Once, during the War of 1812, Gen. Andrew Jackson tried a civilian journalist before a military commission, but the journalist was acquitted on the grounds that as a civilian, he wasn't subject to military justice. (Jackson, on the other hand, was fined $1,000 for contempt.) During the Mexican War, Gen. Winfield Scott made extensive use of military courts, but he obeyed the Articles of War and tried only soldiers in his own ranks who had broken laws.

Yet Frémont and his successor, Henry W. Halleck, believed (incorrectly) that they could legitimately employ military courts in Missouri because they had imposed martial law there. This belief probably stemmed from innocent confusion since, despite a Lincoln administration white paper spelling out the differences between the two concepts, few people understood them.

The defendants who came before these tribunals weren't Confederate soldiers, who, when captured, typically became prisoners of war and weren't put on trial. Rather, the defendants in military court were mainly civilians suspected of aiding the rebels. Gen. Halleck explained the rationale: In Missouri, he said, those burning bridges or buildings weren't "armed and open enemies" but "pretended quiet citizens living on their farms." These civilian rebels couldn't be treated as prisoners of war, but neither could they be entrusted to the local courts, which Halleck deemed "very generally unreliable"—not least because so many locals were likely to sympathize with the South. (International war crimes tribunals, like those used to try the Nazis at Nuremberg after World War II, weren't yet common practice.) So starting in September 1861, Missourians were prosecuted under military tribunals that Union generals established. Lincoln did nothing to deter his generals from doing as they saw fit to subdue Missouri.

Eleven months later, such tribunals were given explicit sanction to operate nationwide. In August 1862, Secretary of War Edwin Stanton, on Lincoln's orders, suspended habeas corpus across the country and decreed that a range of civilian criminals and dissenters would face arrest and trial before military courts. Of the 4,000-plus military trials throughout the war, about 55 percent took place in the border states of Missouri, Maryland, and Kentucky (where the Union military maintained a strong presence and where generals wouldn't trust juries composed of locals). Roughly 32 percent occurred in the Confederate states. The rest occurred in Washington, D.C. (which was also under martial law for some of the war), and the North.

As noted, captured Confederates weren't the usual defendants since they were typically held as prisoners of war. To be sure, after the war, some Confederates were tried before military courts. One Confederate Army officer, Henry Wirz, who ran an inhumane POW camp at Andersonville, Ga., was so tried and was executed for war crimes. The men who conspired with John Wilkes Booth to assassinate Lincoln were also convicted in a military court. On the other hand, civilian courts were often deemed fit to try Confederates. Even Confederate President Jefferson Davis was tried in U.S. federal court, although after President Andrew Johnson pardoned all rebels in 1868, Davis' indictment was dismissed.

The military trials that became most controversial were those of civilians who lived in Union or border states. Their offenses—which were categorized, rather indiscriminately, as "treason," "conspiracy," "rebellion," or other similar crimes—included engaging in guerrilla warfare, spying, avoiding the draft, and even voicing disloyal opinions. These defendants often received less than full justice.

The problem wasn't that the tribunals were kangaroo courts. Staffed by military officers, they did abide by set procedures and sometimes acquitted defendants. Sentences were subject to review by senior officers, death penalties by the president himself. Lincoln himself spared many lives.

But as is typical of military justice, those procedures afforded fewer protections than those of civilian courts. Basic constitutional requirements were ignored. The Army courts had no juries, as the Constitution mandates. Nor did they require a unanimous vote to convict. A majority vote sufficed, except in capital cases, which required a two-thirds vote.