Attorney General Eric Holder addressed the Congressional Black Caucus Thursday, and summarized changes the Department of Justice is taking to end mandatory minimums for "people charged with certain low-level, nonviolent drug offenses." Holder expanded on his initial announcement, made last month, and explained his department’s new policy:  

I am pleased to announce today that the Department has issued new guidance to apply our updated charging policy not only to new matters but also to pending cases where the defendant was charged before the policy was issued but is still awaiting adjudication of guilt.  By reserving the most severe prison terms for serious, high-level, or violent drug traffickers or kingpins, we can better enhance public safety.  We can increase our focus on proven strategies for deterrence and rehabilitation.  And we can do so while making our expenditures smarter and more productive.

As The New York Times reports, Holder issued a memo to prosecutors that the new guidelines apply retroactively:

The policy applies to defendants who meet four criteria: their offense did not involve violence, the use of a weapon, or selling drugs to minors; they are not leaders of a criminal organization; they have no significant ties to large-scale gangs or drug trafficking organizations; and they have no significant criminal histories.

On Thursday, the Justice Department ordered prosecutors to apply the new policy retroactively to defendants who are already in the system but have not yet been sentenced. It was not immediately clear how many pending federal drug cases would be affected.

The policy (that you can read in its entirety)–which relies on prosecutorial discretion–is not truly retroactive, however. Those people already convicted under what Holder referred to as "draconian mandatory minimum sentences" will continue to serve them out.