U.S. Attorney General William Barr addresses the Grand Lodge Fraternal Order of Police's 64th National Biennial Conference at the Ernest N. Morial Convention Center in New Orleans, La. on Aug. 12. Photo: David Grunfeld/The Advocate via AP

Last week, in a speech to the Fraternal Order of Police, Attorney General Barr denounced local prosecutors across the country as "undercutting the police, letting criminals off the hook, and refusing to enforce the law."  He went on to prophesy that this will result in "more crime; more victims."  These comments seemed to target the so-called "progressive prosecutors," whom AG Barr derided as "anti-law enforcement DAs," in particular for policies declining to prosecute cases under specific criminal statutes. This complaint reflects willful blindness to the historical role of prosecutors as local ministers of justice, the sound legal basis for such uses of discretion, and the incontrovertible fact that lawful prosecutorial discretion has been used throughout American history by prosecutors along the entire political spectrum. Notwithstanding the attorney general's objection, most crime is fundamentally a local issue and is best responded to by local, democratically-elected prosecutors.

The American Bar Association sets forth criminal justice standards for the prosecution function, stating: "The prosecutor's office should exercise sound discretion and independent judgment in the performance of the prosecution function." Such discretion can take various forms, from the exercise of mercy based on individual circumstances to the declination to prosecute any cases brought under specific criminal statutes.

The downsides of prosecutorial discretion have been much discussed in the current criminal legal reform movement, including the potential for inconsistent enforcement and disparate racial impact. These concerns are real and warrant great caution. There is an upside to this discretion too, though, and it can inure to the benefit of all local communities. As the highest-ranking elected law enforcement in the majority of counties, prosecutors are in a unique position to respond to local social mores, and the use of discretion is the most efficient way in which the criminal legal system can reflect the preferences of communities.

It is a truism of American history that once a social ill is identified, someone will propose that it be made criminal. This has resulted in all manner of awkward and even absurd criminal laws–be sure not to whisper in church in Delaware or remove seaweed from the beach at night in New Hampshire. Given the complex politics and protracted processes through which state and federal legislation is made, it can take decades to remove ill-advised criminal laws from the books.

Prosecutors need not–and should not–wait for legislators from disparate communities across his or her state to secure legislative change when the local community has voiced a clear preference contrary to an existing statute. Barr's inflammatory rhetoric is not just ahistorical, it's also politically inaccurate. Where some jurisdictions whose socially liberal electorates may decline prosecution of marijuana use or consensual sex work, jurisdictions of all political stripes have long employed their discretion in declining to prosecute sodomy laws, abortion laws, and myriad others.

Indeed, in some states in the union including New York, Oklahoma and Michigan, adultery remains illegal with some states classifying it a felony.  All of the local prosecutors in those states exercise their categorical discretion in declining to prosecute that charge. This is the power of vesting this authority in a local elected official rather than a state legislature or Congress. The attorney general is simply wrong in suggesting that this is a novel phenomenon that is solely the province of progressives.

Traditionally these have been unpublicized internal policies, but it is par for the course in every DA's office that, as a matter of custom, some crimes go unpunished. Mr. Barr seems particularly concerned about the public nature of the exercises of discretion to which he objects in that these district attorneys "have been announcing their refusal to enforce broad swathes of the criminal law."

Unlike the traditional method of simply quietly declining prosecution, these officials are making campaign promises aligned with the values of their communities, then overtly keeping those promises outright. Putting communities on notice about what will and will not be prosecuted is consistent with democratic principles and the commitment to the rule of law.

Across the country, as they always have, prosecutors are responding to their electorates by exercising their discretion to achieve criminal justice outcomes aligned with what their local communities demand at the ballot box. Unlike the appointed attorney general, local DAs do not serve at the will or whim of the president. This is and has always been the power and potential of the local prosecutor.

Lucy Lang is the executive director of the Institute for Innovation in Prosecution at John Jay College of Criminal Justice.