WASHINGTON — Judge John Gleeson hears cases where he used to prosecute them, in the federal courthouse in Brooklyn. There, in 1992, he led the team of prosecutors that put the Mafia boss John J. Gotti in prison for life.

Judge Gleeson is not shy about meting out tough sentences. “Most people, including me,” he wrote in a 2010 decision, “agree that the kingpins, masterminds and midlevel managers of drug trafficking enterprises deserve severe punishment.”

But he has lately been saying that his old employer, the Department of Justice, has stopped living up to its name when it comes to some small-time criminals.

Almost 20 years to the day after delivering his closing argument in the Gotti trial, Judge Gleeson considered the fate of Jamel Dossie, whom he called “a young, small-time, street-level drug dealer’s assistant.”