Alpha dog owners hijacked a public Tribeca pup park nearly a decade ago — installing a lock, charging fees, banning non-member mutts, and enforcing its 22 rules with an iron fist — yet the city never noticed.

Now, the Parks Department is trying to reclaim the dog run for the public, and the snooty pooch privateers are biting back.

The Warren Street Dog Park was originally taken hostage by the Dog Owners of Tribeca (DOOT) in 2008 — after the 92-by-43-foot green space opened between Greenwich and West streets.

A Parks Department rep admitted the takeover somehow “flew under the radar,” probably because the agency “never received any complaints.”

Founders installed a keypad lock on the gate and sent members a secret 4-digit passcode after they paid a $120 annual fee over Paypal on the group’s Website. The code was updated every few months.

Members were to live by 22 strict rules, the first being that non-members were not allowed into the park and members were mandated to chase them out if they tried. If members failed to do so, they were kicked out of the group.

The Post witnessed this exclusionary behavior on Thursday, when two locals were turned away in the span of three hours.

“Could you let me in?” one woman walking a poodle puppy asked.

“No, it’s private!” two members inside the fence barked.

Among the other rules: no children under 12 allowed; no food, and no “socially inept dogs.”

‘You have a group abusing their power and a city agency that’s not being held accountable.’

The non-profit DOOT raked in $83,000 in “membership dues” through 2016, according to their tax filings. They claimed to use the doggie dough for upkeep, such as pressure-washing the blacktop three times a week, maintenance and repairs, insurance and supplies such as poop bags. Money was often left over after each year, the filings show.

One activist criticized both the Parks Department and the park-nappers.

“It’s completely outrageous on both sides,” said Geoffrey Croft, who heads NYC Park Advocates. “You have a group abusing their power and a city agency

that’s not being held accountable.”

A local dog owner said she refuses to pay the fee.

“Why would I pay for something that should be free?” said Liwah Lai, 60, a longtime neighborhood resident who was walking her maltipoo. “It’s unfair and completely absurd. There are so many dog owners in the area like me who need to use the space.”

The founders, however, said the neglectful city forced their hand.

“In the absence of public funds and services, our group will help make sure that this park does not become a stain on the neighborhood,” the group proclaimed in their incorporation papers filed with the state attorney general.

Members said it also allowed them to restore canine order in the neighborhood. “At public dog runs, people let their dogs run wild and act aggressively,” said member Lenore Sherman, 61, who has a golden retriever named Huck. “Here, owners are held accountable for the behavior of their dog.”

One member had no idea the park was public.

“That’s crazy,” said John Ellett, 33, a professional dog-walker. “They even require the dogs to wear special tags, so I thought it was totally private.”

When the dog run first opened, the Parks Department tasked the DOOT to help run the park.

“Dog runs are maintained through barknerships between NYC Parks and community groups,” said Sam Biederman, a Parks spokesman. “NYC Parks dog runs are meant to be open to the public — charging for entrance is prohibited.”

Parks officials snipped the lock Friday, after receiving a complaint. DOOT members were left seething.

“We were quite happy not having Parks involved all these years,” said DOOT board member and leader Shirley Jaffe in an email. Another member said, “No one wants this and we plan to push back.”