His goals include many of the major changes sought by liberal criminal justice reform groups, and in some cases conservative groups as well.

They include eliminating federal incarceration for drug possession and reducing sentences for other drug offenses; legalizing marijuana at the federal level; limiting solitary confinement; and abolishing the death penalty and mandatory minimum sentencing.

Mr. Buttigieg also called for the establishment of several measures specifically addressing policing: tightening the legal standard for police officers to use deadly force; creating a federal database of officers fired from police departments; and persuading states to disclose more data on use of force, line-of-duty deaths, traffic stops and officer misconduct.

Derek Cohen, the director of Right on Crime, a leader in conservative efforts to reform the criminal justice system, estimated that 20 percent of Mr. Buttigieg’s proposals were within the purview of the federal government. The rest are squarely within the authority of state and local officials, he said.

The overwhelming majority of the more than two million inmates in the United States are not in federal custody, but in state and local prisons and jails.

Mr. Buttigieg’s plan includes “some things that show a flicker of brilliance, and other things that seem like chasing down a rabbit hole,” Mr. Cohen said.

He added that, mathematically, one of Mr. Buttigieg’s stated goals — reducing the number of prisoners by 50 percent — would require freeing many violent offenders.