It's the "reindeer police" in Norwegian Lapland, the only force of its kind in the world. Their job is to prevent conflicts between herders and ensure the Far North doesn't turn into the Wild West.
Here, far above the Arctic Circle, the reindeers' grazing grounds can be a source of conflict. Some argue there are just too many reindeer, while harsh weather conditions can make it difficult for the animals to access their main diet, lichen, under the ice-covered snow.
The Sami -- formerly known as Lapps, a term now considered pejorative --have been herding since ancient times, selling the reindeer meat, pelts and antlers which are used in handicrafts.
On the Finnmark plateau in northeastern Norway, where the herds spend the winter grazing after returning from their summer pastures on the coasts, the number of reindeer has been capped at 148,800.
Herders don't always agree on the division of their grazing grounds, with no fences separating them.
Insults, threats, stealing or killing animals, and, more rarely, fisticuffs or gunshots: although it's nearly deserted, the Far North is no stranger to violence.
Enter the "reindeer police".
"If there's a disagreement between one herder and another, we play the go-between and we try to find a solution. We are a kind of peace mediator," Jan Tore Nikolaisen, a former soldier, who has served in the unit for more than a year, tells AFP.
Reindeer in Kautokeino, a town in Finnmark county. Photo: Jonathan Nackstrand/AFP
In 2013, two herders from Kautokeino, the main village in Finnmark, were jailed for beating up a rival who had ventured onto their pasture. They tied him up with a lasso, then left him alone in freezing temperatures and took his snowmobile key.
Another area is so confrontational locals have nicknamed it "the Gaza Strip".
"It has happened that a conflict worsened and became physically violent, although I've never experienced it. But the atmosphere can be tense and people shout insults," says Jim Hugo Hansen, Nikolaisen's colleague.
"Everyone is not always totally pleased, but we usually find a solution so that each herder can go about his business," he adds.
The reindeer police patrol that Mathis Andreas saw approaching his cabin is just paying a courtesy call, it turns out.
Grazing conditions have been good in the area in recent years, making for peaceful coexistence.
But there have been conflicts in the past, admits Andreas, 47, whose family have been herders since the 18th century.
With a smoker's husky laugh, Andreas recalls a harsh expedition he conducted with another man around 30 years ago against three other herders.
The trio had brought their herds to his uncle's pasture and assaulted him with a sharp tool.
"We gave them what they deserved," he recounts, a bit cryptically at first, aware of the presence of his police guest at his side.
The men later moved their animals to a neighbour's pasture further north, where they, he says with a pause, "received a clear message to move promptly".
"They moved even further north, to a third pasture, and there, too, they were roughed up," he says. "They never came back."
"We weren't used to calling the police at the time."
As he speaks, Andreas keeps a close eye on his meal bubbling away on a wood stove. It's reindeer cheek, tongue and rectum. "It's fat, it's very good."
Jim Hugo Hansen and Mathis Andreas look through their binoculars during a patrol. Photo: Jonathan Nackstrand/AFP
The "reindeer police" was created in 1949 to put an end to the widespread poaching that erupted after the Nazis' scorched earth policy left the region devastated.
Today, the 15-member force patrols an area of 56,000 square kilometres more often by snowmobile and quad bike than by car, usually at a distance so as not to frighten the herds.
"Entire weeks can go by without us seeing a reindeer," admits Hansen.
The force's very name is debated, as its members deem it too narrow and misrepresentative.
"We don't just work on reindeer herding," says its chief Inger Anita Øvregård at their headquarters in Alta.
"We also watch over nature and ensure that the public respect the rules, whether it be hunting, fishing or motorised travel," she adds.
And herders find the name stigmatising, claiming it insinuates that crime is more common among them than the rest of society.
"It gives the impression that this police force is here only to deal with these damned herders, but it has many other roles," says Anders Oskal, director of the International Centre for Reindeer Husbandry.
"There are challenges everywhere but, overall, reindeer herders are decent people trying to have a decent life."