New York City’s upside-down justice system is sending a 67-year-old man to prison for four years for owning unlicensed guns — while rapists, stabbers and serial gropers go free.

Charles Foehner was on his way back from buying cigarettes in the wee hours of a May 2023 morning when Cody Gonzalez, 32, a career criminal with 15 prior arrests and a history of mental illness, confronted him.

Foehner says Gonzalez demanded money and cigarettes; surveillance video shows a swaying Gonzalez then charge at Foehner with what he mistook for a knife, but turned out to be a pen.

Foehner shot Gonzalez in the chest multiple times, then called 911.

The elderly man will spend four years in prison after taking a plea deal to avoid getting up to 25 — not for the self-defense killing, which the district attorney didn’t charge him on, but for the roughly 30 illegal weapons Foehner was keeping in his home, which he claims he accumulated in response to crime fears.

There’s little excuse for having an arsenal of illegal guns, and Foehner should undoubtedly face some punishment.

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But why any prison for a senior citizen with no priors? Sure, confiscate his weapons, fine him, put him on probation and warn that reoffending will mean hard time.

Foehner’s almost certainly not an ongoing danger to himself or others — unlike all too many violent repeat offenders who get cut loose with zero prison or even jail time, again and again.

Look at the monster who was let go on the condition that he undergo mental-health treatment after he lured a 14-year-old to his apartment and raped her in 2023, only to pull the same sick stunt with a 15-year-old this year.

Or the sicko who got just 10 years probation and an order to attend a sex-offender treatment program for raping a woman he met on Tinder.

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Or the menace with a history of random attacks who was cut loose on supervised release after he stabbed a stranger on a Bronx train in September, only to slash another man in the face the very next month.

Or the cabbie who Manhattan District Attorney Alvin Bragg declined to prosecute after he was accused of groping two women in the back of his car.

How did all of these true threats to society get lighter punishments than a guy who had illegal guns in his house for decades, and seemingly only used one once for his own self-protection?

Gonzalez himself was a repeat offender who’d likely be alive today if the system had done its job and either jailed him or forced him into treatment for his mental illness.

Other blue cities suffer the same pro-crime lunacy; in Chicago, a madman with 71 prior arrests set a young woman riding the train on fire, prompting even lefty Mayor Brandon Johnson to call it “an absolute failure of our criminal justice” and “mental health institutions.”

A realization that comes too late for the victim who’s fighting for her life.

Serious criminals unleashed time and again on the unsuspecting public, while those who try to defend themselves get locked up: Such is the progressive perversion of “justice.”