The review is a little-noticed element of the National Defense Authorization Act signed into law last month by President Barack Obama. The defense-spending bill calls on the commission to perform several tasks, including an examination of the impact of mandatory-minimum sentencing laws and alternatives to the practice.

Amid cost concerns in recent years, states have tried to reverse the trend. At least 26 states have cut corrections spending recently and at least 17 are closing prisons or reducing their inmate populations, according to the Vera Institute of Justice, a New York nonprofit that studies sentencing and criminal-justice policies.

The U.S. Sentencing Commission, which advises judges on all other sentences, has now been charged with issuing recommendations on mandatory minimums. Any final change in sentencing law would have to come from Congress.

“It’s going to be a massive undertaking,” said the new chairman of the Sentencing Commission, William Sessions III.

Mr. Sessions, who is also the chief federal judge in Vermont, said the review would include everything from determining the effects of minimums on the size of the prison population, to spending and the social impact of the policies. “In my view,” he said, “it’s a very open-ended request.”

The inmate population in federal prisons has risen from 24,000 in 1980 to 209,000 as of Nov. 5. Over the same period, the federal Bureau of Prisons staff has grown from 10,000 to about 36,000 employees.

The commission has pushed for changes in mandatory minimums, such as ending the disparity in sentencing for crimes involving crack-cocaine and powder cocaine. Several proposals are pending in Congress to address the crack-cocaine issue. But the commission has not done a full-scale examination of federal sentencing laws since 1991. At the time, there were only 60 mandatory-minimum laws on the books. Now there are about 170.

According to a limited review released by the commission in July, most mandatory-minimum cases in 2008 concerned drugs or weapons crimes. The review found that 21,023 offenders were convicted of crimes that could have triggered the mandatory-minimum sentence. Many got more lenient sentences for a variety of reasons, including cooperation with authorities.

The commission will examine the effects of mandatory minimums on plea agreements. Critics of the system say the threat of such sentences is used to coerce plea bargains.

Members of the commission have been traveling the country to meet with judges, prosecutors and defense attorneys. Many have pressed the commission to provide alternatives to imprisonment for nonviolent, low-level drug defendants.

James Pasco, executive director of the Fraternal Order of Police, the nation’s largest law-enforcement labor organization, said officers believed it was appropriate to review the system. But he said it shouldn’t happen “in a way that will result in criminals not being held accountable.”

Mary Price, vice president and general counsel for Families Against Mandatory Minimums, said it was too early to tell where the review might lead.

“Certainly from FAMM’s perspective, as much information as the commission can provide on the operation and impact of mandatory minimums can only help us better understand and advocate for their elimination.”