WASHINGTON Attorney General Jeff Sessions instructed federal prosecutors this week to take the most aggressive approach possible against federal criminal defendants. The policy change will result in lengthier prison sentences for drug offenders and likely reverse a recent drop in the federal prison population.

In a memo dated May 10, Sessions wrote federal prosecutors should charge and pursue the most serious, readily provable offense, calling that a core principle of the Justice Departments charging and sentencing policy.

The new policy replaces the approach of the Justice Department during the Obama administration under former Attorneys General Eric Holder and Loretta Lynch . They gave federal prosecutors more leeway to decide when it was appropriate to charge crimes that trigger mandatory minimums, which automatically result in set prison terms.