TROMSO, Norway – Following in an unmarked car, the police took immediate interest in a dark grey minivan with foreign licence plates. The stop-start driving was suspicious. So was the driver’s frantic texting on his cellphone.

When he finally drove up to the sludge-clogged terminal entrance of Tromso airport in Norway, he picked up two passengers.

“As soon as they started driving, we activated the blue lights,” superintendent Lars Holtedahl said, recalling the February operation. “They were caught completely off guard.”

The crime? Working as an unlicensed northern lights tour guide.

The offence might seem minor to outsiders, but to the people of Tromso, a small Norwegian city above the Arctic Circle, such guides have become virtually Public Enemy No. 1.

Unregulated tour operators have created havoc in Tromso, which is perfectly perched on the fjords between snow-capped mountains to view the aurora borealis, the colour-streaked light display over the North Pole.

For much of the year, Tromso is ...