At the state level, the changes appear to be driven as much by budget problems as by ideology. Corrections budgets have quadrupled in the last 20 years, to more than $50 billion in 2008, according to the Pew Center on the States.
With 2.3 million people in prison and another 5.1 million on probation or parole, states have considered a variety of options to reduce prison populations.
Not everyone sees a significant departure from previous drug policies. John Walters, President George W. Bush's drug czar, said he has not seen indications of a major shift in federal drug policy, saying Bush supported drug courts and treatment.
"The perception may be different. The fact is they would not be very different in emphasis," he said.
Walters said the Obama administration's apparently more tolerant approach to marijuana enforcement, which has not been spelled out in detail, would be a mistake. Walters has argued that the drug remains a serious threat.
"If we don't deal with marijuana, we're not taking seriously the substance abuse problem in the United States," he said. "Everybody would like to push marijuana aside but you can't do it. It is still a serious health problem."
Washington has been one of most liberal states in its approach to marijuana, and is one of 13 in the country with a medical marijuana law. In Seattle, where Kerlikowske is the top cop, voters passed a city ordinance in 2003 making marijuana the lowest law enforcement priority. The city, where crime is at a 40-year low, is also home to the annual Hempfest.
Drug reform activists and people who have worked with Kerlikowske said that while he has not been a champion of Seattle's reforms -- he opposed the 2003 ordinance, arguing that the law was unnecessary -- he has taken a pragmatic approach to drug control and maintains a good relationship with local drug reform activists.
"I expect he will be the first to admit that this is not a challenge that can be addressed by law enforcement alone," said King County Prosecuting Attorney Dan Satterberg. "You can't arrest your way out of the drug problem."
Kerlikowske, president of the Major Cities Chiefs Association, is former deputy director for the Justice's Department's Office of Community Oriented Policing Services. He was police chief in Fort Pierce and Port St. Lucie, Fla., and police commissioner in Buffalo, N.Y., before moving to Seattle in 2000.
Kerlikowske has experienced the problem of drugs in own family. His stepson, Jeffrey, 39, has been arrested several times on drug and other charges, police records show. He is currently in jail in Florida for a probation violation.
"Our nation's drug problem is one of human suffering, and as a police officer, but also in my own family, I have experienced the effects that drugs can have on our youth, our families and our communities," Gil Kerlikowske said when his nomination was announced.
Jeffrey Kerlikowske, in a brief phone interview from jail, declined to discuss his relationship with his father, other than to say that they haven't spoken in more than 10 years.
"My life has nothing to do with him," he said.
He "taught me a lot of good qualities about perseverance and tenacity. He was one of reasons I chose to go into the Marine Corps," Jeffrey Kerlikowske said of his father.
As young police officer, "When everyone else was out bowling at night, he was putting himself through college," he said.