Attorney General Jeff Sessions overturned the sweeping criminal charging policy of former attorney general Eric H. Holder Jr. and directed his federal prosecutors Thursday to charge defendants with the most serious, provable crimes carrying the most severe penalties.

The Holder memo, issued in August 2013, instructed his prosecutors to avoid charging certain defendants with drug offenses that would trigger long mandatory minimum sentences. Defendants who met a set of criteria such as not belonging to a large-scale drug trafficking organization, gang or cartel, qualified for lesser charges — and in turn less prison time — under Holder’s policy.

But Sessions’s new charging policy, outlined in a two-page memo and sent to more than 5,000 assistant U.S. attorneys across the country and all assistant attorneys general in Washington, orders prosecutors to “charge and purse the most serious, readily provable offense” and rescinds Holder’s policy immediately.

The Sessions memo marks the first significant criminal justice effort by the Trump administration to bring back the toughest practices of the drug war, which had fallen out of favor in recent years with a bipartisan movement to undo the damaging effects of mass incarceration.