The message Attorney General Mukasey is sending by appointing a career federal prosecutor within his chain of command to investigate the destruction of CIA interrogation tapes is that Mr. Mukasey is not going to repeat the errors of his predecessors by abdicating his own responsibilities. In another Bush administration case involving the CIA, Attorney General Ashcroft let his deputy, James Comey, appoint a Chicago prosecutor, Patrick Fitzgerald, as “Special Counsel independent of the supervision or control of any officer of the Department,” as Mr. Comey’s letter to Mr. Fitzgerald put it. The letter delegated to Mr. Fitzgerald “all the authority of the attorney general.”

The Comey-Ashcroft default created a runaway train that the president ultimately had to stop, using his power of clemency to stop I. Lewis “Scooter” Libby from being sent to prison in connection with the disclosure of the identity of a CIA official, Valerie Plame Wilson. Nearly a decade earlier, President Clinton and Attorney Reno dodged their responsibilities by naming Robert B. Fiske Jr. as the independent counsel for Whitewater. Mr. Fiske was succeeded by Kenneth Starr, then Robert Ray, who ended up getting Mr. Clinton to admit publicly that he “knowingly violated” a judge’s discovery orders by giving false answers to questions about Monica Lewinsky in Paula Jones’s sexual harassment lawsuit.

The contrast in this case is clear. Unlike Mr. Fitzgerald, who answered essentially to no one, and unlike Messrs. Fiske, Starr, and Ray, who answered to a panel of judges under a law that has since expired without being renewed, the prosecutor in the CIA tape destruction investigation, John Durham, “will report to the Deputy Attorney General, as do all United States Attorneys in the ordinary course,” Mr. Mukasey said yesterday. The deputy attorney general reports to Mr. Mukasey, who reports to President Bush. In other words, the executive branch is handling its own affairs, which is as it should be under the separation of powers established by our constitution.

We were among the first to suggest Mr. Mukasey for the job of attorney general, and we’ve been warning of the dangers of runaway special prosecutors since the Iran-Contra days. It’s not clear to us that there was a crime committed with the destruction of the interrogation tapes, but if there was, let it be someone in the normal chain of command who decides whether the matter is worthy of bringing to a grand jury. It is Mr. Bush, after all, who has the responsibility of defending America from attack by the terrorists and of using the information gained in these interrogations to protect us all.