Harry Liang and his friends were wrapping up an overnight canoe trip at the Delaware Water Gap National Recreation Area in June when they were approached by a group of National Park Service rangers.

Thinking the rangers were just dropping by to say hello, Liang waved at them as he and his friends waded in a nearby river.

But instead, the rangers began screaming expletives at the group because they were not packing up their campsite 10 minutes ahead of an apparent noon check-out time, demanding they get out of the water and line up on the beach.

“One ranger yelled at a woman in a wet bathing suit to get down on the dirt floor when she couldn't find a chair. Then another ranger yelled at the dog owners to leash the dogs or he was going to shoot them,” Liang told the Washington Examiner. “This specific ranger sounded psychopathic. He actually threatened to kill the dog, a puppy cocker spaniel only a few months old.”

“The rangers proceeded to make us sit in a circle in our bathing suits as we watched them search all of our bags and tents without permission,” he said. “We didn't know what to do.”

The “humiliating” half-hour search yielded just two citations, Liang said.

"It was a traumatic experience for everyone,” he said. “They treated us like we were terrorists, like we had committed some serious crime.”

While Liang said he and his friends later filed a complaint, he doesn’t believe the rangers involved received any form of punishment.

“The irony of the whole situation was that the leader of the park rangers that harassed us was training the other rangers. Apparently he wanted to use us as an example of how to search and harass,” Liang said.

Liang’s story is not unlike many that describe rangers’ harsh treatment of minor offenses.

From a 60-year-old woman who says she was frisked and jailed overnight because, with a Breathalyzer reading of .06, rangers considered her a danger, to a man who claims he was thrown against the hood of his car and handcuffed after exiting his stopped vehicle due to a medical emergency, anecdotes of abuse have emerged in local media, blogs and travel websites.

Law enforcement agencies like the park rangers gauge their success by the number of arrests or violations they secure, Paul Larkin, a senior legal research fellow at the Heritage Foundation, told the Examiner.

“The more that you can show you’ve done, the greater the likelihood that you can get increased appropriations, increased assets and the like, even if all you’ve done is make little regulatory violations into crimes,” he said. “They’ll respond that way if you give them that incentive."

Larkin said the tendency to over-criminalize can seep into an agency's culture.

Rangers have come under fire for heavy-handed enforcement in the past. In 2012, a ranger in the Golden Gate National Recreation Area shot a local man with a stun gun following a dispute over his unleashed dog.

Rep. Jackie Speier, D-Calif., called for an investigation into the National Park Service after the incident, which she called a "gross reaction to the infraction committed."

“Excessive use of force by park rangers cannot be condoned,” Speier told the Examiner. “The National Park Service must reign in excessive use of police power by their rangers. Park rangers should work to be more like Smokey the Bear, not Rambo.”

Speier, who is a member of the House Committee on Government and Oversight Reform, pushed the Interior Department inspector general for another National Parks investigation in September over allegations that Lassen Volcanic National Park staff covered up misconduct in the case of a nine-year-old boy's 2009 death.

“I wasn’t satisfied with either investigation," she said. "Since I sent my letter, the Inspector General informed my office that they have reopened their investigation of misconduct. Our park facilities need to be safe, and when those responsible for safety fail, they should face the consequences.”

Jurisdiction varies among parks depending on the legislation that created them. In Yellowstone and Yosemite, the federal government has exclusive authority.

In other parks, local law enforcement can work with the park service.

A member of a search-and-rescue team in Canyonlands National Park who asked not to be named recounted an incident in which a ranger tried to prevent a helicopter on a rescue mission from landing where it needed to because it might “bother the grass.”

After the team leader overrode the ranger's demands and landed, the ranger refused to let the team step off the trail as they headed to rescue an injured person.

The team member said locals share a general sense that rangers in his park are “overzealous.”

“You’ve got a bunch of people that almost want to be cops, but they forget what they’re doing,” the member said. “They’re enforcing things like pulling off the road and crushing grass or stepping off the trail, and stuff that’s just absurd.”

Jeffrey Olson, spokesman for the National Park Service, told the Examiner such complaints are “isolated incidents.”

“If we have an incident where somebody makes a complaint about the actions of a member of the National Park Service, we take that very seriously, whether its a law enforcement ranger or anybody else in the National Park Service,” Olson said.

Individual parks record the number of violations they issue in different ways, but the numbers are rising in some. In 2005, the Yellowstone prosecutor’s office handled 574 cases for offenses committed mostly in that park and in nearby Grand Teton National Park.

By 2011, the office dealt with 1,012 such cases, not including the “large majority” of violations that required only a fine, according to the Justice Department.

What’s more, the list of banned activities seems to be growing. In June, the park service made it a crime to fly “unmanned aircraft” — a category that includes model planes — in Yellowstone, lest the “wilderness character and values” of the park be disturbed.

Violators could face jail time or hefty fines if they choose to defy the ban.