Gravel v. United States, which arose out of Senator Mike Gravel's attempt to publicize the Pentagon Papers, concerned the scope of the immunity conferred upon a legislator and his aide under article I, section 6, of the United States Constitution. This provision, commonly called the "speech or debate clause," provides that "for any Speech or Debate in either House, [United States Senators or Representatives] shall not be questioned in any other Place." Gravel is one of the few Supreme Court interpretations of this clause.
Michigan Law Review,
Immunity Under the Speech or Debate Clause for Republican and from Questioning About Sources,
Mich. L. Rev.
Available at: https://repository.law.umich.edu/mlr/vol71/iss6/7