During Reconstruction, Congress expanded the habeas corpus jurisdiction of the federal courts in order to prevent state authorities from imprisoning federal officials or freedpeople arbitrarily. The 1867 statute made habeas corpus available to any person “restrained of his or her liberty in violation of the constitution, or of any treaty or law of the United States,” thereby extending the writ to state prisoners claiming that their detention violated a federal right. Just as significantly, habeas corpus became a post-conviction remedy, as federal courts exercised the power to free individuals that had been tried and convicted by state tribunals.

See also:

Habeas Corpus Jurisdiction