To protect the privilege of resorting in a proper case to proceedings by habeas corpus the federal constitution as well as the constitutions of the various states contain provisions regulating the suspension of the writ. The provision of the federal constitution is that " The privilege of the writ of habeas corpus shall not be suspended unless when in cases of rebellion or invasion the public safety may require it" (Art. I, § 9, ¶ 2). Such suspension is involved in the declaration of martial law (see above, § 114), and is only proper when it becomes necessary temporarily to subject the exercise of civil authority to the military power. It has been the subject of much discussion whether without legislative authority the president may suspend the writ on his own judgment in cases of rebellion or invasion (Ex parte Merry man and Ex parte MilHgan). But he may be authorized to do so by statute, as was done in 1863, 1866, and 1867.

In the absence of any suspension of the writ on account of such emergency as is contemplated by the constitution, the right to the writ for the purpose of having determined by judicial authority the lawfulness of imprisonment or other deprivation of personal liberty is a constitutional right, and the prohibition against its suspension is regarded as one of the personal guaranties of civil liberty. In the constitutional history of England the final establishment of the right to a judicial inquiry as to the lawfulness of any arrest or detention, even under the authority of the king himself, was the final step in the complete recognition of individual liberty and the subordination of the executive authority to the limitations imposed by constitutional government. The right was finally established in England by the Habeas Corpus Act, passed in 1679, which is regarded as one of the fundamental charters of civil liberty.