WASHINGTON — Attorney General Jeff Sessions is expected to soon toughen rules on prosecuting drug crimes, according to people familiar with internal deliberations, in what would be a major rollback of Obama-era policies that would put his first big stamp on a Justice Department he has criticized as soft on crime.

Mr. Sessions has been reviewing a pair of memos issued by his predecessor, Eric H. Holder Jr., who encouraged federal prosecutors to use their discretion in what criminal charges they filed, particularly when those charges carried mandatory minimum penalties.

The policy under consideration would return the department to the era of George W. Bush. In 2003, Attorney General John Ashcroft ordered the nation’s prosecutors to bring the most serious charges possible in the vast majority of cases, with limited exceptions. Mr. Sessions could, however, craft his own policy that does not go quite so far; a draft is still being reviewed.

Mr. Sessions, who cut his teeth as a young prosecutor in Alabama during the height of the crack epidemic, came to office promising to make being tough on crime a top priority, and his new guidance on charging and sentencing would be the strongest articulation yet of his emphasis on a law-and-order agenda.