What it is, why it's important, and under what circumstances it can be denied?
Over the years, the writ of habeas corpus has generally been used as a tool by those imprisoned to force the government to show to a neutral judge why it has the jurisdiction and authority to detain someone. It is important to note that, a prisoner seeking a writ of habeas corpus is not asking the federal reviewing court to determine his guilt or innocence, but merely whether his incarceration is supported by the law. In state court convictions, only a fundamental constitutional error in a trial will compel the granting of the great writ.
That tool, as expressed in the Constitution, can be suspended in certain situations. For example, General Andrew Jackson declared martial law in New Orleans during the War of 1812 and arrested people. A federal court judge issued a writ of habeas corpus, but Jackson blocked their release. Jackson was fined $1000 for contempt of court after refusing to produce the prisoners. Incidentally, Jackson lobbied Congress for a refund of the $1000 fine he paid, which was granted in 1844.
During the Civil War, President Lincoln suspended habeas corpus in areas where militia activity and rioting threatened civil society. In 1864, several men were accused of planning to steal Union Weapons, and they were convicted and sentenced to die in military courts. However, the executions were not set until 1865, when the civil courts had been restored. The Supreme Court ruled that that writ of habeas corpus could not be suspended when the civil courts were functioning.
Two main court cases in 1942 and 1950 set the stage for today’s debate over who can access habeas corpus. In 1942, the Supreme Court ruled in that unlawful combatant saboteurs could be denied habeas corpus and tried by military commission, making a distinction between lawful and unlawful combatants. In 1950, the Court denied access to habeas corpus for nonresident aliens captured and imprisoned abroad in a US-administered foreign court.
Today, the debate centers around those people imprisoned as “enemy combatants” held at Guantanamo Bay. The Bush administration previously utilized statutes passed by Congress to detain, indefinitely, and without any review, those defendants who were deemed “enemy combatants.” However, in 2004, the Supreme Court ruled that U.S. Citizens still maintained the right to habeas corpus, and in 2006, the Court held that the military tribunals set up by the administration were unconstitutional. Today, the fate of those held at Guantanamo, and those labeled as enemy combatants is unclear.