Filed at 7:14 p.m. ET

WASHINGTON (AP) -- Chief Justice William H. Rehnquist on Monday rebuffed two Democratic senators who questioned Justice Antonin Scalia's impartiality in an appeal involving Scalia's friend and hunting partner, Vice President Dick Cheney.

Sens. Joe Lieberman of Connecticut, a presidential candidate, and Patrick Leahy of Vermont asked Rehnquist last week to clarify disqualification practices after Scalia acknowledged joining Cheney on a recent duck hunting trip.

The Louisiana trip earlier this month came shortly after the Supreme Court agreed to review a lower court's decision requiring the White House to identify members of the vice president's energy task force. Scalia also had dinner with Cheney in November, about two months after the administration asked the justices to overrule the lower court.

Rehnquist said any suggestion that Scalia should recuse himself ``is ill considered.''

Rehnquist, a Republican put on the high court by Richard Nixon in 1972 and made chief justice by Ronald Reagan in 1986, said that while justices often consult with colleagues when they are considering recusing themselves from a case, there is no formal procedure.

``It has long been settled that each justice must decide such a question for himself,'' he wrote in a letter sent to Lieberman, Leahy and each of the other court justices.

Rehnquist did not give an opinion about whether Scalia should step down from hearing the case, but made clear that it was up to Scalia -- and no one else -- to make that decision. After the case is over ``anyone at all is free to criticize the action of a justice,'' Rehnquist wrote.

Leahy said Monday that Rehnquist's letter confirms that the Supreme Court, unlike federal appeals courts and district courts, has no recusal procedure or oversight system. He also defended the timing of the letter.

``Because Supreme Court decisions cannot be reviewed, waiting until after a case is decided needlessly risks an irreversible, tainted result and a loss of public confidence in our nation's highest court,'' Leahy said.

Ethics expert Steven Lubet of Northwestern University said Rehnquist's response is not surprising, because it follows long-standing court tradition. But he said it will probably not silence critics, including people who were angry at the court's 5-4 Bush v. Gore decision that effectively called the deadlocked presidential election for George W. Bush. Scalia voted with the majority.

The case in question involves Cheney's request to keep private the details of closed-door White House strategy sessions that produced the administration's energy policy. The administration is fighting a lawsuit brought by watchdog and environmental groups that contend that industry executives, including former Enron chairman Ken Lay, helped shape the administration's energy policy.

The court will hear arguments in the case this spring, and the two lawmakers told Rehnquist that ``when a sitting judge, poised to hear a case involving a particular litigant, goes on a vacation with that litigant, reasonable people will question whether that judge can be a fair and impartial adjudicator of that man's case.''

Scalia, named to the court by Reagan, is one of the court's staunchest conservatives. He has said there is no reason to question his ability to judge the case fairly.

Scalia did step aside in another major case at the Supreme Court this term. He will not participate when the court decides whether it is unconstitutional for public school children to pledge their allegiance to ``one nation under God.'' The father who challenged the Pledge of Allegiance had sought Scalia's recusal because the justice told a religious group last year that lawmakers rather than judges are better suited to decide the pledge question.

The energy case is In re Cheney, 03-475.