By DOUGLAS A. BERMAN AND HARLAN PROTASS

May 7, 2013 Wall Street Journal - There are few topics on which leading Democratic and Republican voices agree these days. But the recently introduced Justice Safety Valve Act of 2013—which would authorize federal judges to impose prison terms below statutory mandatory minimums in some cases—represents a new bipartisan effort at addressing America's overcrowded prisons and bloated budget. Passage of the act, though, will depend on President Obama and his Justice Department getting behind it.

Mr. Obama has long talked about reforming federal mandatory minimum sentencing laws. During the 2007 presidential campaign, he promised that if he were elected his administration would review those provisions to see "where we can be smarter on crime and reduce the blind and counterproductive warehousing of nonviolent offenders."

After Mr. Obama gained the White House, federal prosecutor Sally Quillian Yates testified for the Justice Department at a May 2010 hearing before the U.S. Sentencing Commission that the Obama administration believes "there are real and significant excesses in terms of the imprisonment meted out for some offenders" under existing mandatory minimum laws. Just last month, Attorney General Eric Holder lamented that "too many people go to too many prisons for far too long for no good law enforcement reason" and that federal mandatory minimums "too often bear no relation to the conduct at issue, breed disrespect for the system, and are ultimately counterproductive."

Yet President Obama still has not proposed or championed any major reforms. So the bipartisan Justice Safety Valve Act now presents his administration with an opportunity to make good on his pledges. By throwing his weight behind this act, and urging Congress to make it apply retroactively to those still imprisoned based on mandatory-minimum provisions, the president could demonstrate that his campaign promises of hope and change were more than political slogans.

Congress began embracing harsh mandatory-minimum laws in the 1980s, in part over frustration with judges who seemed lax in sentencing, but mostly because of the crack epidemic poisoning the country. Legislators believed that long prison terms could help deter drug crimes—for instance, five years for five grams of crack, roughly a couple of sugar cubes in weight. Lawmakers thereafter frequently backed new mandatory minimums, which enabled them to claim on the campaign trail that they were "tough on crime."

Though good political rhetoric, mandatory-minimum sentencing laws have proven to be bad policy. They transfer enormous power to prosecutors—who choose the charges to bring—and federal judges regularly complain of being required to impose excessively long prison terms on nonviolent offenders. These laws also fueled a federal-prison population explosion—with its consequent financial costs, ruined lives and broken families.

The U.S. Sentencing Commission reports that nearly 20,000 defendants—most of whom are nonviolent drug offenders—face long, mandated minimum prison terms each year, at a "warehousing" cost of nearly $30,000 annually for each inmate. About half of all federal prisoners doing time today—a population of more than 218,000—are incarcerated for narcotics offenses. President Obama's fiscal year 2013 budget requests $6.8 billion for federal prisons alone, more than a quarter of the entire Justice Department budget.

The Justice Safety Valve Act, recently introduced by Sens. Patrick Leahy (D., Vt.) and Rand Paul (R., Ky.), and to the House by Reps. Robert C. "Bobby" Scott (D., Va.) and Thomas Massie (R., Ky.), could help reduce the millions of taxpayer dollars wasted keeping thousands of people sentenced under mandatory minimum laws locked up. The bill would enable federal judges to consider when or whether a mandatory-minimum sentence serves legitimate law-enforcement purposes given the particular circumstances of the crime and defendant. Judges could impose prison terms below the statutory minimums only when they explain, through an on-the-record, reviewable opinion, that a shorter term is sufficient to serve the express goals of the criminal justice system set out by Congress.

As described by Julie Stewart, the president and founder of Families Against Mandatory Minimums, the bill would "ensure that judges use our scarce prison beds and budget to keep us safe from truly violent offenders." According to Sen. Leahy, the bill would help rein in ballooning prison budgets, which mean "less money for . . . law enforcement" and "less funding for crime prevention programs and prisoner re-entry programs."

No single piece of legislation can reform all the laws and practices that have resulted in the federal government now imprisoning more Americans than were incarcerated by all 50 states a few decades ago.

But bipartisan support and sponsorship of the Justice Safety Valve Act highlights that prominent lawmakers on both sides of the aisle agree—at this time of lean budgets, sequester cuts and overcrowded prison facilities—that the current federal sentencing scheme is neither fair nor effective, and that mandatory-minimum sentencing laws lie at the heart of the problem.

President Obama's vocal support of this bill would signal a real commitment to using his bully pulpit to advocate on behalf of significant reform proposals. If he does not, the president's failure to champion sentencing reform may become his most lasting federal criminal-justice legacy.

Mr. Berman is a law professor at the Moritz College of Law at The Ohio State University and the co-author of "Sentencing Law & Policy" (WoltersKluwer 3d ed., 2013). Mr. Protass is a criminal-defense lawyer in New York and an adjunct professor at the Benjamin N. Cardozo School of Law, where he teaches about sentencing.