The federal prison population is on the decline, but a new attorney general who talks tough on drugs and crime and already has indicated a looming need for private prison cells seems poised to usher in a reversal of that trend. Jeff Sessions, a former federal prosecutor sworn in this month as the country’s chief law enforcement officer, signaled at his confirmation hearing – and during private meetings in his first days on the job – that he sees a central role for the federal government in combating drug addiction and violence as well as in strict enforcement of immigration laws.