First the basics, from Michael Dorf:

The Constitution nowhere expressly mentions executive privilege. Presidents have long claimed, however, that the constitutional principle of separation of powers implies that the Executive Branch has a privilege to resist certain encroachments by Congress and the judiciary, including some requests for information.

. . . [In 1807], the issue of executive privilege arose in court. Counsel for Aaron Burr, on trial for treason, asked the court to issue a subpoena duces tecum--an order requiring the production of documents and other tangible items--against President Thomas Jefferson, who, it was thought, had in his possession a letter exonerating Burr.

After hearing several days of argument on the issue, Chief Justice John Marshall issued the order commanding Jefferson to produce the letter. Marshall observed that the Sixth Amendment right of an accused to compulsory process contains no exception for the President, nor could such an exception be found in the law of evidence. In response to the government's suggestion that disclosure of the letter would endanger public safety, Marshall concluded that, if true, this claim could furnish a reason for withholding it, but that the court, rather than the Executive Branch alone, was entitled to make the public safety determination after examining the letter.

. . . Presidents often assert executive privilege even if the information or documents sought are not matters of national security. They argue that some degree of confidentiality is necessary for the Executive Branch to function effectively. Key advisers will hesitate to speak frankly if they must worry that what they say will eventually become a matter of public record.

The Supreme Court considered this argument in the 1974 case of United States v. Nixon. . . . The Court recognized "the valid need for protection of communications between high Government officials and those who advise and assist them in the performance of their manifold duties." It noted that "[h]uman experience teaches that those who expect public dissemination of their remarks may well temper candor with a concern for appearances and for their own interests to the detriment of the decisionmaking process. Nonetheless, the Justices concluded that the executive privilege is not absolute. Where the President asserts only a generalized need for confidentiality, the privilege must yield to the interests of the government and defendants in a criminal prosecution. . . .

The most recent case on the issue was the Cheney Energy Task Force case. Here were the highlights. First, the basic doctrine is restated:

It is well established that "a President's communications and activities encompass a vastly wider range of sensitive material than would be true of any 'ordinary individual.' " United States v. Nixon, 418 U. S., at 715. Chief Justice Marshall, sitting as a trial judge, recognized the unique position of the Executive Branch when he stated that "[i]n no case ... would a court be required to proceed against the president as against an ordinary individual." United States v. Burr, 25 F. Cas. 187, 192 (No. 14,694) (CC Va. 1807). See also Clinton v. Jones, 520 U. S. 681, 698-699 (1997) ("We have, in short, long recognized the 'unique position in the constitutional scheme' that [the Office of the President] occupies" (quoting Nixon v. Fitzgerald, 457 U. S. 731, 749 (1982))); 520 U. S., at 710-724 (Breyer, J., concurring in judgment). As United States v. Nixon explained, these principles do not mean that the "President is above the law." 418 U. S., at 715. Rather, they simply acknowledge that the public interest requires that a coequal branch of Government "afford Presidential confidentiality the greatest protection consistent with the fair administration of justice," ibid., and give recognition to the paramount necessity of protecting the Executive Branch from vexatious litigation that might distract it from the energetic performance of its constitutional duties.

Then the typical judical dancing begins:

Nixon cannot bear the weight the Court of Appeals puts upon it. First, unlike this case, which concerns respondents' requests for information for use in a civil suit, Nixon involves the proper balance between the Executive's interest in the confidentiality of its communications and the "constitutional need for production of relevant evidence in a criminal proceeding." Id., at 713. The Court's decision was explicit that it was "not ... concerned with the balance between the President's generalized interest in confidentiality and the need for relevant evidence in civil litigation ... . We address only the conflict between the President's assertion of a generalized privilege of confidentiality and the constitutional need for relevant evidence in criminal trials." Id., at 712, n. 19. The distinction Nixon drew between criminal and civil proceedings is not just a matter of formalism. As the Court explained, the need for information in the criminal context is much weightier because "our historic[al] commitment to the rule of law ... is nowhere more profoundly manifest than in our view that 'the twofold aim [of criminal justice] is that guilt shall not escape or innocence suffer.' " Id., at 708-709 (quoting Berger v. United States, 295 U. S. 78, 88 (1935)).

To which I say HA! Yes, the extra concern about fair trials in criminal contexts is duly noted from the Rehnquist Court, with the likes of Scalia, Thomas et al. I tell you, I do not know how these folks can look at themselves, the nonsense they write sometimes.

Do you think CONGRESS' duties will weigh in a decision, and it will never come to this I assure you, on whether Rove has to testify? Will Scalia, Thomas et al think it important? Maybe in the NEXT Administration. Not this one.

But there is more nonsense:

A party's need for information is only one facet of the problem. . . . This is not a routine discovery dispute. The discovery requests are directed to the Vice President and other senior Government officials who served on the NEPDG to give advice and make recommendations to the President. The Executive Branch, at its highest level, is seeking the aid of the courts to protect its constitutional prerogatives. As we have already noted, special considerations control when the Executive Branch's interests in maintaining the autonomy of its office and safeguarding the confidentiality of its communications are implicated. This Court has held, on more than one occasion, that "[t]he high respect that is owed to the office of the Chief Executive ... is a matter that should inform the conduct of the entire proceeding, including the timing and scope of discovery," Clinton, 520 U. S., at 707, and that the Executive's "constitutional responsibilities and status [are] factors counseling judicial deference and restraint" in the conduct of litigation against it, Nixon v. Fitzgerald, 457 U. S., at 753. Respondents' reliance on cases that do not involve senior members of the Executive Branch, see, e.g., Kerr v. United States Dist. Court for Northern Dist. of Cal., 426 U. S. 394 (1976), is altogether misplaced.

Is Karl Rove a HIGH official? How come I think this SCOTUS would declare him so?

Well, you know the rest. If ever there was a time to view these things as a Legal Realist, the issue of Executive Privilege is the one. Personally, I think there is NO law on this really, it is all politics. And it will be politics, not law, that decides whether Rove and Co. testify before Congress.

But as long as we are reviewing the Cheney case, it is still fun to read Justice Scalia's explanation of how his being friends with Cheney and going duck hunting with him is not a recusing circumstance:

For five years or so, I have been going to Louisiana during the Court's long December-January recess, to the duck-hunting camp of a friend whom I met through two hunting companions from Baton Rouge, one a dentist and the other a worker in the field of handicapped rehabilitation. The last three years, I have been accompanied on this trip by a son-in-law who lives near me. Our friend and host, Wallace Carline, has never, as far as I know, had business before this Court. He is not, as some reports have described him, an "energy industry executive" in the sense that summons up boardrooms of ExxonMobil or Con Edison. He runs his own company that provides services and equipment rental to oil rigs in the Gulf of Mexico.

During my December 2002 visit, I learned that Mr. Carline was an admirer of Vice President Cheney. Knowing that the Vice President, with whom I am well acquainted (from our years serving together in the Ford administration), is an enthusiastic duck-hunter, I asked whether Mr. Carline would like to invite him to our next year's hunt. The answer was yes; I conveyed the invitation (with my own warm recommendation) in the spring of 2003 and received an acceptance (subject, of course, to any superseding demands on the Vice President's time) in the summer. The Vice President said that if he did go, I would be welcome to fly down to Louisiana with him. (Because of national security requirements, of course, he must fly in a Government plane.) That invitation was later extended-- if space was available--to my son-in-law and to a son who was joining the hunt for the first time; they accepted. The trip was set long before the Court granted certiorari in the present case, and indeed before the petition for certiorari had even been filed.

We departed from Andrews Air Force Base at about 10 a.m. on Monday, January 5, flying in a Gulfstream jet owned by the Government. We landed in Patterson, Louisiana, and went by car to a dock where Mr. Carline met us, to take us on the 20-minute boat trip to his hunting camp. We arrived at about 2 p.m., the 5 of us joining about 8 other hunters, making about 13 hunters in all; also present during our time there were about 3 members of Mr. Carline's staff, and, of course, the Vice President's staff and security detail. It was not an intimate setting. The group hunted that afternoon and Tuesday and Wednesday mornings; it fished (in two boats) Tuesday afternoon. All meals were in common. Sleeping was in rooms of two or three, except for the Vice President, who had his own quarters. Hunting was in two- or three-man blinds. As it turned out, I never hunted in the same blind with the Vice President. Nor was I alone with him at any time during the trip, except, perhaps, for instances so brief and unintentional that I would not recall them--walking to or from a boat, perhaps, or going to or from dinner. Of course we said not a word about the present case. The Vice President left the camp Wednesday afternoon, about two days after our arrival. I stayed on to hunt (with my son and son-in-law) until late Friday morning, when the three of us returned to Washington on a commercial flight from New Orleans. . . .

Scalia is a trip. A lift down on a government plane for him and his son and son-in-law and he also insists he had no private time with Cheney?

Anyway, given Cheney's shooting abilities as demonstrated to another "friend", what I would really like to know is if Scalia has ever asked to go hunting with Cheney again?