A 17-year-old reputed Brooklyn gangbanger who was cut loose despite an attempted murder rap and two open gun cases is finally in jail after getting nabbed with another loaded gun, sources told The Post.

Jahquell James was initially held on $50,000 bail in the 2021 shooting of a bystander, but a Brooklyn judge freed him in January to attend an alternative sentencing program — despite him having two gun arrests still pending, according to sources and court records.

“How do we know if these programs are working?” one law enforcement source said Thursday. “What does success look like?

“This kid was following the program while carrying a loaded gun,” he said. “That is a failure.”

Said another source, “he blew it.”

James could even have walked away with just probation in the attempted murder case if he had completed the 18-month program.

But on Tuesday, cops nabbed him in Bedford-Stuyvesant with a loaded 9 mm handgun.

The next day he was arraigned and finally ordered held without bail in a city youth facility pending his next court appearance, records show.

James was just 15 in 2020 when he was first picked up with a loaded gun and was shipped directly to Family Court as a juvenile without even getting arraigned, the sources and court records show.

That case was still pending when he was busted again on April 21, 2021 for allegedly shooting another teenager in the foot in Crown Heights, the records show.

In that case, James was arraigned in Brooklyn court, but was sent to Youth Court and his case remained sealed while it was pending.

He remained locked up at the Crossroads Juvenile Center in Brooklyn until January when he pleaded guilty pending completion of an alternative sentencing program.

Brooklyn Youth Court Judge Craig Walker dropped the bail so the troubled teen could attend the program, which could have ended with a sentence of probation.

Sources said James is a reputed member of the Rich Fam street gang.

A spokesman for the state Office of Court Administration declined to comment on James’ case Thursday because it involves juvenile cases.

Walker made headlines last year when another teenage gangbanger, 18-year-old Courtney Yeates, was picked up on a gun charge after the judge freed him for doing well in school.

Yeates, who had at least nine prior arrests, had four open cases at the time. His record included a felony robbery conviction and a grand larceny/auto bust.

Earlier this week The Post reported a similar criminal justice fail in the case of a 25-year-old career criminal who shot and wounded a city cop during a shootout in the Bronx.

Rameek Smith, who was mortally wounded in the exchange of gunfire with police, was free while awaiting sentencing on a 2020 felony gun case.

A Brooklyn judge ignored prosecutors’ request to hold Smith on $50,000 bail and allowed him to remain free to attend a two-year mental health program.