Attorney General Eric Holder announced Monday that he is changing Justice Department policy so that "low-level, nonviolent" drug offenders will no longer face mandatory minimum prison sentences.

Holder announced the overhaul during a speech to the American Bar Association in San Francisco.

"Too many Americans go to too many prisons for far too long, and for no truly good law enforcement reason," Holder said.

The attorney general said he's "mandated" that certain low-level offenders "who have no ties to large-scale organizations, gangs, or cartels" will not be charged with offenses that impose stiff mandatory minimum sentences. Rather, he said, they will be charged with offenses that carry sentences "better suited to their individual conduct."

The announcement drew praise from some in Congress, including one vocal administration critic. Sen. Rand Paul, R-Ky., said he was "encouraged" by the announcement and that minimum sentences for non-violent offenders "do not serve public safety."

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Mandatory minimum prison sentences, a product of the government's war on drugs that began in the 1980s, limit the discretion of judges to impose shorter prison sentences.

The unanswered question is how each of the 94 U.S. Attorneys offices around the country will implement changes, given the authority of prosecutors to exercise discretion in how they handle their criminal cases.

African-Americans and Hispanics likely would benefit the most from a change. African-Americans account for about 30 percent of federal drug convictions each year and Hispanics account for 40 percent, according to Marc Mauer, executive director of the Sentencing Project, a non-profit group involved in research and policy reform of the criminal justice system.

If state policymakers were to adopt similar policies, the impact of changes at the state level could be even broader, said Mauer. Currently, about 225,000 state prisoners are incarcerated for drug offenses, according to the U.S. Bureau of Justice Statistics.

Federal prisons are operating at nearly 40 percent above capacity and hold more than 219,000 inmates -- with almost half of them serving time for drug-related crimes and many of them with substance use disorders. In addition, 9 million to 10 million prisoners go through local jails each year.

Holder praised state and local law enforcement officials for already instituting some of the types of changes Holder says must be made at the federal level.

Aggressive enforcement of federal criminal laws is necessary, but "we cannot simply prosecute or incarcerate our way to becoming a safer nation," Holder said.

Holder said mandatory minimum sentences "breed disrespect for the system."

Sens. Dick Durbin, D-Ill., Patrick Leahy, D-Vt., Mike Lee, R-Utah, and Paul, R-Ky., have introduced legislation aimed at giving federal judges more discretion in applying mandatory minimums to certain drug offenders.

Holder said new approaches -- which he is calling the "Smart On Crime" initiative -- are the result of a Justice Department review he launched early this year.

The attorney general said some issues are best handled at the state or local level and said he has directed federal prosecutors across the country to develop locally tailored guidelines for determining when federal charges should be filed, and when they should not.

The attorney general said 17 states have directed money away from prison construction and toward programs and services such as treatment and supervision that are designed to reduce the problem of repeat offenders.

In Kentucky, legislation has reserved prison beds for the most serious offenders and refocused resources on community supervision. The state, Holder said, is projected to reduce its prison population by more than 3,000 over the next 10 years, saving more than $400 million.

He also cited investments in drug treatment in Texas for non-violent offenders and changes to parole policies which he said brought about a reduction in the prison population of more than 5,000 inmates last year. He said similar efforts helped Arkansas reduce its prison population by more than 1,400. He also pointed to Georgia, North Carolina, Ohio, Pennsylvania and Hawaii as states that have improved public safety while preserving limited resources.

Holder also said the department is expanding a policy for considering compassionate release for inmates facing extraordinary or compelling circumstances, and who pose no threat to the public. He said the expansion will include elderly inmates who did not commit violent crimes and who have served significant portions of their sentences.

The Associated Press contributed to this report.