Des Moines police said Prior had 2 pounds of methamphetamine and $17,690 in cash when he was arrested in May 1995.

Prior, then 46, refused an offer of a lighter sentence in exchange for information about other meth dealers.

U.S. District Judge Ronald Longstaff called the mandatory life prison sentence unjust. He begged Prior to help authorities, which would allow the judge to reduce the sentence levied under the federal "three strikes" law. That law requires a life sentence for anyone with two or more previous felony drug convictions.

Prior was convicted in 1992 in Arizona and six years earlier in California. He has been held at a medium-security prison in Greenville, Ill.

Prior wrote an open letter about the danger of drugs, which was distributed last year to more than 1,700 schools in California and various athletic organizations, Holliday said.

Groups that oppose mandatory prison sentences applauded Bush's decision, but said the clemency highlights "systematic injustice" that sends low-level drug offenders to prison.

Mandatory minimum sentences account for about 202,000 offenders in federal prisons, according to Families Against Mandatory Minimums.

Prior and his family "will be eternally grateful for a fresh start, and, judging from past commutation grantees, he will be a law-abiding, taxpaying citizen who contributes to society," said Julie Stewart, president of the group.