The framers of our Constitution envisioned that in the exercise of their authorities, the two political branches would assert their prerogatives against each other. A process of negotiation and accommodation between the branches is what one would expect. That process isn't elegant, but a push-pull between the branches doesn't necessarily mean that anything is wrong.

What is going wrong today, however, is the take-it-or-leave-it position of the White House.

The struggle between Congress and the executive branch over the requested testimony of White House officials regarding the removal of eight U.S. attorneys is playing out in the political arena. In fact, the political arena is where the contours of these prerogatives are largely shaped, rather than in our courts. While executive privilege is based in constitutional principles of the separation of powers and the authority of the president over the executive branch, and the privilege has been recognized by the Supreme Court, its scope has been largely determined outside the judicial process.

President Bush's counsel not inappropriately started by seeking to shield high-level White House advisers from compelled testimony before Congress. The White House offered the officials for private interviews by lawmakers and their staffs, so long as there are no oaths, transcripts, follow-up interviews or queries delving into White House discussions. Lawmakers have rejected that offer as insufficient to permit Congress to exercise fully its oversight and legislative roles, and congressional committees have authorized the issuance of subpoenas.

Out of respect for the separation of powers, Congress should not ordinarily call on such officials for testimony but should leave such officials to devote their attention to their duties for the president. This rationale no longer has force for those who have left the White House, such as Harriet Miers, but even then, communications with the president or internal White House communications about the president's decision to dismiss his appointees should usually be shielded from disclosure. Presidents need candid advice from their counselors, and respecting the privilege enhances the likelihood of such candor.

But Congress has duties and responsibilities in our constitutional system as well, and the president has an equal responsibility to respect Congress' important and legitimate interests in this matter. Serious questions have been raised about whether illegitimate considerations played into those dismissal decisions. These are questions Congress should be exploring. While any president has the authority to fire his or her appointees, including U.S. attorneys, the independence of our prosecutors from improper political (not policy) influence is a bedrock principle of our criminal justice system.

We don't know exactly what happened, but enough questions have been raised by the e-mails that have been disclosed and officials' changing stories to establish that Congress — and the American people — are entitled to know more. When Congress has already received information and testimony that raises serious questions about possible wrongdoing, the White House counsel's offer — a closed-door session that may not be recorded, even by a transcript, and on the condition that Congress has only one bite at the apple, no matter what it may subsequently learn — is simply inadequate. Executive privilege is an important and essential constitutional principle, but it is not the only important principle at issue here.

Congress can be too aggressive in intruding on executive prerogatives. When I was counsel to the president, we were deluged with subpoenas, many of which were issued unilaterally by a committee chair and served on us without even the courtesy of a phone call first. So much for respecting a co-equal branch or engaging in a process of accommodation. I testified before Congress twice, under oath and pursuant to subpoena, on White House e-mail reconstruction. Even after the change in administrations, I testified under oath when Congress sought information about presidential pardons. (Once, the president asserted a privilege when my testimony was sought regarding earlier pardons.) Too often during that period, Congress failed to show proper restraint in seeking information from the White House.

But the executive can also be too aggressive in asserting its prerogatives in the face of a legitimate need of Congress. Each branch should vigorously seek to protect its legitimate powers, and each branch should recognize the legitimacy of the others' concerns. The White House's current insistence that its restrictive offer is nonnegotiable prevents the process from working as it should.

Beth Nolan is a litigation partner in the Washington-based law firm Crowell & Moring LLP. She was counsel to the president from September 1999 to January 2001 and served in the Justice Department's Office of Legal Counsel as deputy assistant attorney general from 1996 to 1999. She wrote this commentary for the Washington Post.