Libby has already paid his fine of $250,400 to the District of Columbia clerk of court, reports CBS News.
"I don't know what Arkansan is for chutzpah, but this is a gigantic case of it," presidential spokesman Tony Snow said.
Rep. John Conyers, D-Mich., has scheduled hearings on Mr. Bush's commutation of Libby's 2½-year sentence.
"Well, fine, knock himself out," Snow said of Conyers. "I mean, perfectly happy. And while he's at it, why doesn't he look at January 20th, 2001?"
In the closing hours of his presidency, Clinton pardoned 140 people, including fugitive financier Marc Rich.
The former president tried to draw a distinction between the pardons he granted, and Mr. Bush's decision to commute Libby's 30-month sentence in the CIA leak case.
"I think there are guidelines for what happens when somebody is convicted," Clinton told a radio interviewer Tuesday. "You've got to understand, this is consistent with their philosophy; they believe that they should be able to do what they want to do, and that the law is a minor obstacle."
Sen. Clinton, seeking the Democratic presidential nomination, said the Libby decision "was clearly an effort to protect the White House. ... There isn't any doubt now, what we know is that Libby was carrying out the implicit or explicit wishes of the vice president, or maybe the president as well, in the further effort to stifle dissent."
Former Vice President Al Gore said he found Mr. Bush's decision "disappointing" and said he did not think it was comparable to Clinton's pardons.
"It's different because in this case the person involved is charged with activities that involved knowledge of what his superiors in the White House did," Gore said on NBC's "Today" show Thursday.
Snow also tried to clear up confusion about Libby's probation. While commuting Libby's sentence in terms of prison time, Mr. Bush left in place his two years of supervised release. But supervised release — a form of probation — is only available to people who have served prison time. Without prison, it's unclear what happens next.
Snow said the White House view was this: "You treat it as if he has already served the 30 months, and probation kicks in. Obviously, the sentencing judge will figure out precisely how that works."
U.S. District Judge Reggie B. Walton, earlier this week, said the law "does not appear to contemplate a situation in which a defendant may be placed under supervised release without first completing a term of incarceration."
He gave Libby's attorneys and Special Prosecutor Patrick Fitzgerald until Monday to respond.