MR. CHIEF JUSTICE BURGER delivered the opinion of the Court: . . .

On March 1, 1974, a grand jury of the United States District Court for the District of Columbia returned an indictment charging seven named individuals with various offenses, including conspiracy to defraud the United States and to obstruct justice. Although he was not designated as such in the indictment, the grand jury named the President, among others, as an unindicted coconspirator. On April 18, 1974, upon motion of the Special Prosecutor, a subpoena duces tecum was issued pursuant to Rule 17(c) [of the Federal Rules of Criminal Procedure] to the President by the United States District Court and made returnable on May 2, 1974. This subpoena required the production, in advance of the September 9 trial date, of certain tapes, memoranda, papers, transcripts of other writings relating to certain precisely identified meetings between the President and others. The Special Prosecutor was able to fix the time, place, and persons present at these discussions because the White House daily logs and appointment records had been delivered to him. On April 30, the President publicly released edited transcripts of 43 conversations; portions of 20 conversations subject to subpoena in the present case were included. On May 1, 1974, the President’s counsel filed a "special appearance" and a motion to quash the subpoena under Rule 17(c). This motion was’ accompanied by a formal claim of privilege. At a subsequent hearing, further motions to expunge the grand jury’s action naming the President as an unindicted coconspirator and for protective orders against the disclosure of the information were filed or raised orally by counsel for the President.

On May 20, 1974, the District Court denied the motion to quash and the motions to expunge and for protective orders. 377 F.Supp. 1326. It further ordered "the President or any subordinate officer, official, or employee with custody or control of the documents or objects subpoenaed," to deliver to the District Court, on or before May 31, 1974, the originals of all subpoenaed items, as well as an index and analysis of those items, together with tape copies of those portions of the subpoenaed recordings for which transcripts had been released to the public by the President on April 30. . . .

On May 24, 1974, the President filed a timely notice of appeal from the District Court order, and the certified record from the District Court was docketed in the United States Court of Appeals for the District of Columbia Circuit. On the same day, the President also filed a petition for writ of mandamus in the Court of Appeals seeking review of the District Court order.

Later on May 24, the Special Prosecutor also filed, in this Court, a petition for a writ of certiorari before judgment. On May 31, the petition was granted with an expedited briefing schedule. On June 6, the President filed, under seal, a crosspetition for writ of certiorari before judgment. This cross-petition was granted June 15, 1974, and the case was set for argument on July 8, 1974.

The threshold question presented is whether the May 20, 1974, order of the District Court was an appealable order and whether this case was properly "in" the Court of Appeals when the petition for certiorari was filed in this Court. . . . [The Court answers yes.]

In the District Court, the President’s counsel argued that the court lacked jurisdiction to issue the subpoena because the matter was an intrabranch dispute between a subordinate and superior officer of the Executive Branch and hence not subject to judicial resolution. . . . Our starting point is the nature of the proceeding for which the evidence is sought—here a pending criminal prosecution. It is a judicial proceeding in a federal court alleging violation of federal laws and is brought in the name of the United States as sovereign. Under the authority of Art. II, § 2, Congress has vested in the Attorney General the power to conduct the criminal litigation of the United States Government. 28 U.S.C. § 516. It has also vested in him the power to appoint subordinate officers to assist him in the discharge of his duties. 28 U.S.C. §§509, 510, 515, 533. Acting pursuant to those statutes, the Attorney General has delegated the authority to represent the United States in these particular matters to a Special Prosecutor with unique authority and tenure. The regulation gives the Special Prosecutor explicit power to contest the invocation of executive privilege in the process of seeking evidence deemed relevant to the performance of these specially delegated duties.

So long as this regulation is extant it has the force of law. . . .

Here, . . . it is theoretically possible for the Attorney General to amend or revoke the regulation defining the Special Prosecutor’s authority. But he has not done so. So long as this regulation remains in force the Executive Branch is bound by it, and indeed the United States as the sovereign composed of the three branches is bound to respect and to enforce it. Moreover, the delegation of authority to the Special Prosecutor in this case is not an ordinary delegation by the Attorney General to a subordinate officer: with the authorization of the President, the Acting Attorney General provided in the regulation that the Special Prosecutor was not to be removed without the "consensus" of eight designated leaders of Congress. . . .

In light of the uniqueness of the setting in which the conflict arises, the fact that both parties are officers of the Executive Branch cannot be viewed as a barrier to justiciability. It would be inconsistent with the applicable law and regulation, and the unique facts of this case, to conclude other than that the Special Prosecutor has standing to bring this action and that a justiciable controversy is presented for decision. . . .

In a case such as this, . . . where a subpoena is directed to a President of the United States, appellate review, in deference to a coordinate branch of Government, should be particularly meticulous to ensure that the standards of Rule 17(c) have been correctly applied. From our examination of the materials submitted by the Special Prosecutor to the District Court in support of his motion for the subpoena, we are persuaded that the District Court’s denial of the President’s motion to quash the subpoena was consistent with Rule 17(c). We also conclude that the Special Prosecutor has made a sufficient showing to justify a subpoena for production before trial. The subpoenaed materials are not available from any other source, and their examination and processing should not await trial in the circumstances shown.

Having determined that the requirements of Rule 17(c) were satisfied, we turn to the claim that the subpoena should be quashed because it demands "confidential conversations between a President and his close advisors that it would be inconsistent with the public interest to produce." The first contention is a broad claim that the separation of powers doctrine precludes judicial review of a President’s claim of privilege. The second contention is that if he does not prevail on the claim of absolute privilege, the court should hold as a matter of constitutional law that the privilege prevails over the subpoena duces tecum.

In the performance of assigned constitutional duties each branch of the Government must initially interpret the Constitution, and the interpretation of its powers by any branch is due great respect from the others. The President’s counsel, as we have noted, reads the Constitution as providing an absolute privilege of confidentiality for all Presidential communications. Many decisions of this Court, however, have unequivocally reaffirmed the holding of Marbury v. Madison, 1 Cranch 137 (1803), that "[i]t is emphatically the province and duty of the judicial department to say what the law is."

No holding of the Court has defined the scope of judicial power specifically relating to the enforcement of a subpoena for confidential Presidential communications for use in a criminal prosecution, but other exercises of power by the Executive Branch and the Legislative Branch have been found invalid as in conflict with the Constitution. Powell v. McCormack, 395 U.S. 486 (1969); Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579 (1952). . . . Since this Court has consistently exercised the power to construe and delineate claims arising under express powers, it must follow that the Court has authority to interpret claims with respect to powers alleged to derive from enumerated powers. . . .

We therefore reaffirm that it is the province and duty of this Court "to say what the law is" with respect to the claim of privilege presented in this case.