Thanks to sensible law-enforcement policies, violent crime rates dropped by half in the United States over the past three decades. Although increases occurred in 2015-16, the rates again dropped during the first two years of the Trump Administration.But reductions in crime are neither automatic nor inevitable. They are the result of federal, state and local law enforcement and prosecutors working together to enforce the laws.Unfortunately, a trend is emerging that could threaten the hard-fought progress in public safety. A small but troubling number of state and local prosecutors are vowing that they will not enforce entire categories of core criminal offences as part of a misguided experiment in “social justice reform”.A prosecutor has a vital role: to enforce the law fairly and keep the public safe. These purportedly progressive district attorneys, however, are shirking that duty in favour of unfounded decriminalisation policies that they claim are necessary to fix a “broken” system.The Philadelphia district attorney, for instance, has in effect decriminalised thefts of up to $500. Boston’s district attorney actually campaigned, before her election last year, with a list of crimes her office would not prosecute — including drug distribution, “larceny under $250”, receiving stolen property, trespassing, malicious destruction of property and resisting arrest.In San Francisco, the new DA has vowed not to prosecute “quality of life” crimes such as public urination and prostitution. And the new DA in Fairfax County said during his campaign that he wouldn’t prosecute as a felony any larceny below $1,500, ignoring the state threshold of $500, would not seek cash bail for felonies and would charge unlawful immigrants more leniently than US citizens for the same crimes to circumvent the immigration consequences of the crimes.While the Trump Administration is dedicated to enforcing federal criminal law, as shown by the record number of violent crime prosecutions during the past two years, not every state crime is prosecutable as a federal offence.Contrary to the belief that inspires these so-called social justice policies, the “system” is not broken.Just as violent crime rates are near historic lows, national incarceration rates have also fallen 13 per cent over the past decade, hitting a 20-year low, according to a 2019 report by the Bureau of Justice Statistics.Those who still believe that certain criminal laws hinder “social justice” should vote for a legislature, not a prosecutor, to address their concerns. Outright non-enforcement of the law is an affront to the separation of powers. The legislative branch writes the law. The judicial branch interprets the law. And the executive branch — of which these prosecutors are a part — enforces the law.Prosecutors have discretion to decide what individual cases to bring and how best to resolve them. But the categorical refusal to enforce basic laws geared towards public safety goes far beyond prosecutorial discretion, violates the duty to enforce the laws as passed by the legislature and flies in the face of the fundamental concept that no one part of government exercises total control.Prosecutorial policies that disregard core criminal laws, and the inflammatory rhetoric that often accompanies those practices, also erode respect for the rule of law. These prosecutors risk demeaning the very institutions they are appointed to lead and fuelling mistrust by promoting false narratives about the criminal-justice system and law enforcement.The prosecutors are essentially flipping the script, casting criminals as victims and police as villains. This distortion is not only demoralising to law enforcement, but also emboldens hostility towards both the rule of law and those entrusted with enforcing it.Perhaps the gravest injustice of this “social justice” is the lack of respect it shows for crime victims. Consider the example of a woman in Boston who was attacked in 2017 while walking her dog. The victim was left unconscious, sustained a traumatic brain injury and faces years of recovery.Over the victim’s objection, the district attorney, in line with these social-reform initiatives, sanctioned a plea agreement that allowed the attacker to plead to a misdemeanour and avoid prison time.Revealingly, the Boston DA has said that she represents “not just the victim, but the defendant and the community”. The problem is not with the prosecutor representing the “community”, but with representing the “defendant”.Indeed, DAs are supposed to represent the community against the defendant. Public defenders and other defence lawyers represent the alleged violators. Prosecutors who think they are defence lawyers are in the wrong job. Victims deserve better.Prosecutors who have misunderstood their obligations are giving a free pass to many wrongdoers and are devaluing victims. That is not justice.To preserve the gains made in public safety, state and local partners need to work hand in hand with federal law enforcement to faithfully enforce the law and protect the American people.• Jeffrey A. Rosen is the deputy attorney-general of the United States