In an unusual 21-page memorandum, he rejected a request by the Sierra Club. The environmental group said it was improper for Scalia to take a hunting trip with Cheney while the court was considering whether the White House must release information about private meetings of Cheney's energy task force.
Scalia said the remote Louisiana hunting camp used for a duck hunting and fishing trip "was not an intimate setting."
The justice said he was guilty only of hunting with a friend and taking a free plane ride to get there. "If it is reasonable to think that a Supreme Court justice can be bought so cheap, the nation is in deeper trouble than I had imagined," Scalia wrote.
"My recusal is required if ... my impartiality might reasonably be questioned," Scalia wrote. "Why would that result follow from my being in a sizable group of persons, in a hunting camp with the vice president, where I never hunted with him in the same blind or had other opportunity for private conversation?"
Given the circumstances of the trip, Scalia wrote, the only possible reason for recusal would be his friendship with Cheney.
"A rule that required members of this court to remove themselves from cases in which the official actions of friends were at issue would be utterly disabling," Scalia wrote.
Many Supreme Court justices get their jobs "precisely because they were friends of the incumbent president or other senior officials," he wrote.
Supreme Court justices, unlike judges on other courts, decide for themselves if they have conflicts, and their decisions are final.
The Sierra Club is suing to get information about private meetings of Cheney's energy task force. The court agreed in December to hear the case, and three weeks later Scalia and Cheney flew together on a government jet to the hunting camp of a multimillionaire oil-services tycoon.
Pressure on Scalia to stay out of the case had mounted, with calls from dozens of newspapers for the conservative Reagan administration appointee to recuse himself to protect the court's image of impartiality.
The Sierra Club asked for Scalia's recusal in February, pointing to the "American public's great concern about the continuing damage this affair is doing to the prestige and credibility of this court."
There was no obligation for Scalia to explain his decision, but he did in the 21-page memo. He said he will recuse himself when "on the basis of established principles and practices, I have said or done something which requires this course." He said the hunting trip to Louisiana was planned before the energy case reached the court.
Those "established principles and practices" do not require or even permit him to step aside in the Cheney case, Scalia wrote.
The Supreme Court arguments in the case are scheduled for April 27.
In addition to the Sierra Club, Democrats in Congress and some legal ethicists have called on Scalia to stay out of the case.
Scalia noted in his memo that he has stepped aside in another case this term — one testing the constitutionality of the Pledge of Allegiance in public schools. The decision came after he criticized the lower court ruling during a speech at a religious rally.
For the first time, Scalia revealed details of his trip with Cheney.
Scalia said he was the go-between to invite Cheney to hunt with a Scalia friend, Wallace Carline, who owns an oil rig services firm, Scalia wrote. Scalia and Cheney are friends from their days working in the Ford administration, Scalia noted.
"I conveyed the invitation, with my own warm recommendation, in the spring of 2003 and received an acceptance," Scalia wrote.
When the time came for the trip, Scalia and Cheney flew together, accompanied by one of Scalia's sons and a son-in-law, Scalia wrote.