Attorney General Jeff Sessions’ office sent out a letter late Thursday to the nation’s federal prosecutors instructing them to pursue the most serious charges possible against most criminal suspects.

The move will send more people to prison and for much longer terms by triggering mandatory minimum sentences.

Officials at the Department of Justice said the new guidelines are a direct rebuttal of policies implemented under President Obama’s attorney general, Eric Holder.

The memo is already being referred to as “the Sessions Memo.” The 94 U.S. attorneys were instructed in the memo to “charge and pursue the most serious and readily provable offense.”

These cases often carry the longest sentences.The memo also brings back into effect mandatory minimum sentences, which are expected to increase prosecutions and the prison population.

Holder, who served under the Obama administration, implemented the “Smart on Crime” drug sentencing policy that focused on not incarcerating people who committed low level non-violent crimes.

READ MORE: Putin congratulates Moon on election as South Korean president

The Obama administration used the “Smart on Crime” policy to combat what they believed was a high number of prosecutions of non-violent drug offenders. DOJ officials call it a “false narrative” and say unless a gun is involved, most of those cases aren’t charged period.

Officials say Holder’s “Smart on Crime” policy “convoluted the process,” and left prosecutors applying the law unevenly, which they said “is not Justice.”

Critics of the shift say it will revive the worst aspects of the drug war. But Sessions has said a spike in violence in some big cities shows the need for a return to tougher tactics.