IN THEIR struggle over documents relating to the replacement of US attorneys, the president and Congress have downplayed a critical point: The doctrine of executive privilege remains a constitutional wilderness, and courts have done little to sort out the problem.
Because the law is so wide open, both President Bush and the congressional Democrats have made plausible arguments. In any judicial proceeding, the outcome would be hard to predict; neither side has reason for great confidence.
The Constitution does not refer to executive privilege at all, and some "strict constructions" believe that the whole idea is a constitutional myth. But presidents have long insisted that in order to exercise their constitutional authority, they need to be able to keep their own communications confidential.
The Supreme Court finally accepted this claim during the Watergate dispute in 1974 -- but President Nixon lost anyway. The court agreed that the Constitution gives the president a privilege against mandatory disclosure of his communications, at least when he is speaking with his closest advisers. But the court also ruled that the privilege is qualified rather than absolute, and that it can be overcome when "weighty and legitimate competing interests" are at stake. In the Nixon case, the court concluded that the need for evidence in a criminal trial is sufficient to overcome the privilege.
Since the Nixon decision, lower courts have struggled with two different questions. The first involves the scope of the privilege: Is it restricted to communications involving the president (and vice president) personally, or does it include everyone in the White House or even executive branch? The second involves the weight: What must a congressional committee show to overcome the privilege?
On the first question, the Bush administration argues that Congress cannot obtain communications by White House staff involving a decision ultimately to be made by the president himself. And indeed, a federal court of appeals has said that executive privilege covers all "communications authored or solicited and received by members of an immediate White House adviser's staff" giving advice "to the president on the particular matter to which the communications relate."
So if Harriet Miers, Bush's former counsel, produced documents on replacing the US attorneys, the president can reasonably argue that executive privilege applies. Congress does have some responses. It might contend that some of the relevant communications come from people outside of the executive branch. In general, these communications were neither "authored" nor "solicited and received" by White House staff. Unsolicited outside communications may not fall within the privilege.
Congress might also note that the White House has said that President Bush did not decide, personally, to replace the US attorneys. Congress might contend that the privilege applies only to communications culminating in the president's personal decision.
Even if the privilege applies, Congress can argue that it is overcome here, because there is legitimate reason to suspect serious wrongdoing on the part of the executive branch. It would be a grave matter -- conceivably even an impeachable offense -- if the White House used its power over US attorneys to punish those who prosecuted Republicans or declined to prosecute Democrats. If Congress has reason to suspect that something like this happened, it might be able to overcome the privilege, just as in the Nixon case.
The president's best answer is that this is not a judicial proceeding and that Congress has not demonstrated anything like sufficient need for these materials. The Department of Justice argues that Congress has received "thousands of documents and dozens of hours of testimony already." The department adds that Congress must do more than to say, in a general way, that it fears wrongdoing or that the materials "are of public import"; it must show that they are "demonstrably critical" to Congress' effort to exercise its constitutional role.
Congress' strongest reply is that the evidence reveals a real need for the documents, which are indispensable to establish whether a genuine misuse of executive power has occurred. Congress might add that its own lawmaking prerogatives are at stake. If partisan politics has affected the decision to replace US attorneys, it might seek to enact corrective legislation.
In arguing for inherent authority to engage in torture, and for the power to make war without congressional approval, the Bush administration has made some extravagant arguments about executive power. But the president's authority to resist congressional subpoenas has never been well defined. If the issue gets to court, anything can happen.
Cass R. Sunstein is a law professor at the University of Chicago.