Though they reach radically different conclusions on the process that ought to attend the present proceeding, the parties begin on common ground. All agree that, absent suspension, the writ of habeas corpus remains available to every individual detained within the United States. U. S. Const., Art. I, \ufffd9, cl. 2 ("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"). Only in the rarest of circumstances has Congress seen fit to suspend the writ. See, e.g., Act of Mar. 3, 1863, ch. 81, \ufffd1, 12 Stat. 755; Act of April 20, 1871, ch. 22, \ufffd4, 17 Stat. 14. At all other times, it has remained a critical check on the Executive, ensuring that it does not detain individuals except in accordance with law. See INS v. St. Cyr, 533 U. S. 289, 301 (2001). All agree suspension of the writ has not occurred here. Thus, it is undisputed that Hamdi was properly before an Article III court to challenge his detention under 28 U. S. C. \ufffd2241. Brief for Respondents 12. Further, all agree that \ufffd2241 and its companion provisions provide at least a skeletal outline of the procedures to be afforded a petitioner in federal habeas review. Most notably, \ufffd2243 provides that "the person detained may, under oath, deny any of the facts set forth in the return or allege any other material facts," and \ufffd2246 allows the taking of evidence in habeas proceedings by deposition, affidavit, or interrogatories.

The simple outline of \ufffd2241 makes clear both that Congress envisioned that habeas petitioners would have some opportunity to present and rebut facts and that courts in cases like this retain some ability to vary the ways in which they do so as mandated by due process. The Government recognizes the basic procedural protections required by the habeas statute, Id., at 37-38, but asks us to hold that, given both the flexibility of the habeas mechanism and the circumstances presented in this case, the presentation of the Mobbs Declaration to the habeas court completed the required factual development. It suggests two separate reasons for its position that no further process is due.

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