Attorney General Jeff Sessions has ordered federal prosecutors to pursue the toughest possible charges and sentences against crime suspects, he announced Friday, reversing Obama administration efforts to ease penalties for some nonviolent drug violations.

The drastic shift in criminal justice policy, foreshadowed during recent weeks, is Mr. Sessions’s first major stamp on the Justice Department, and it highlights several of his top targets: drug dealing, gun crime and gang violence.

…

David Alan Sklansky, a law professor at Stanford University who specializes in criminal justice, disagreed in part. “Not everybody who falls within the letter of the criminal prohibition is somebody who deserves that kind of criminal punishment,” he said. “It’s not about excusing people or condoning criminal behavior; it’s a question of trying to figure out how much punishment is enough and at what point are you piling on needlessly and at great cost.”

…

Mr. Sklansky said it was unclear how dramatic an impact Mr. Sessions’s new policy may have.

“Prosecutors in the field appropriately pay attention to and try to follow the directions they receive from Washington,” he said. “A reversal or replacement of the Holder memo will be interpreted by many prosecutors in the field as a direction to be more aggressive to use mandatory minimum penalties against low-level nonviolent drug offenders.