During the Civil War, President Lincoln declared martial law with regard specifically to “rebels and insurgents” and certain other disloyal individuals. Although Lincoln limited the application of martial law (it did not apply to the general population), in 1866 the Supreme Court ruled, in a case called Ex parte Milligan, that his order to try such persons by military commission was illegal where civilian courts remained open and operating.
In its decision, the Court laid out criteria for invocation of martial law:
If, in foreign invasion or civil war, the courts are actually closed, and it is impossible to administer criminal justice according to law, then, on the theatre of active military operations, where war really prevails, there is a necessity to furnish a substitute for the civil authority, thus overthrown, to preserve the safety of the army and society; and as no power is left but the military, it is allowed to govern by martial rule until the laws can have their free course.
And, the Court said, “As necessity creates the rule, so it limits its duration.” The Court warned of allowing this extraordinary measure under other circumstances: “Civil liberty and this kind of martial law cannot endure together; the antagonism is irreconcilable; and, in the conflict, one or the other must perish.”
Elizabeth Goitein: The alarming scope of the president’s emergency powers
The Court apparently failed to consider the possibility that the courts might be closed by military order. In such a case, of course, no one would be left to judge the legitimacy of the military’s actions.
The objective criteria set out by the Court—the presence of war, actual insurrection or invasion, effective closure of courts, displacement of civil authorities, and no alternative to protect the Army and society—left plenty of room for judgment about when martial law could be proclaimed. Yet they revealed the kind of extreme conditions that might justify its use.
Martial law was declared a number of times in the late nineteenth and early twentieth centuries at the state level, by governors acting as commanders in chief of their militias or national guards. Most often the declarations resulted from labor disputes. In a 1903 miners’ strike, for example, Colorado Governor James Peabody declared martial law in San Miguel County, where Telluride is located. He closed the saloons, imposed a curfew, censored the press, collected guns, and suspended habeas corpus, although the civil courts remained open. He also ordered state troops to arrest and detain Charles Moyer, the president of the Western Federation of Miners. In the Supreme Court’s 1909 decision in Moyer v. Peabody, Justice Oliver Wendell Holmes upheld the legality of Peabody’s use of martial law, writing that “the governor’s declaration that a state of insurrection existed is conclusive of that fact … When it comes to a decision by the head of the state upon a matter involving its life, the ordinary rights of individuals must yield to what he deems the necessities of the moment.”