Skiing through the vast Portes du Soleil network, just south of Geneva, I stopped short at a notice at the bottom of the Mossettes chairlift that read "French-Swiss border: You must carry your identity card".
This may come as news to skiers who cross the border on a whim to reach the cruisy red and blue runs of the sunny south-facing Swiss slopes. And at The Wall – a steep, heavily mogulled black run – border formalities are not at the top of skiers' minds as they cross the frontier mostly on their backsides.
"Technically, it's correct," says local customs officer Jérôme Phalippou. "You must be able to present your papers at any time."
I meet Jérôme in the historic customs house in Châtel, on the French side. Happily, he hadn't pulled me in for questioning. After 13 years' active service, he stopped his rounds in 2009 when his patrol was disbanded and has since been working to open the customs house as a new museum, which it did last summer.
For the contrebandiers, the fact that these ski routes crossed the border was all important. They were the smugglers who until the 1950s dodged patrols and even bullets to bring cigarettes, coffee and other contraband to France from Switzerland.
Jérôme is also a brilliant cartoonist and has illustrated many of the contrebandiers' stories. Along with original artefacts, reconstructions with mannequins, a mystery for visitors to solve and audioguides in English, these bring to life many of the high-mountain dramas. Equipped with the contrebandiers' secrets, adults and children can embark on their own adventures exploring the smugglers' routes.
The door opens behind us and we were joined by André Crépy, 80 years old and Châtel's mayor for three decades. It turns out he is also a former smuggler. Curiously the contrebandiers had a certain respectability in Savoie, which became part of France only in 1860. The region enjoyed free trade with Switzerland until the concession was abruptly withdrawn after the First World War. And during the Second World War the contrebandiers worked in tandem with the Resistance, with the young André sending coded messages between the two. By the 1940s virtually every young man who wasn't a customs officer was a part-time smuggler – and some were both.
"You were caught twice, I believe," says Jérôme, which André answers with a chuckle.
"Ah yes, being a contrebandier really got the adrenalin going," André recalls, describing how he once skied 50km on a deliberately circuitous route to the Swiss village of Morgins and back in Tintin-style golfing trousers. These weren't purely for fashion. On his return journey they were stuffed full of cigarette papers.
Payment to the Swiss might be in gold coins hidden in skis. Or food, though women smuggling butter under their dresses were found out when a thoughtful customs officer sent them to stand by a radiator to warm up.
Even livestock could be traded. André describes how they would get pigs drunk to keep them quiet. "It wasn't very economical," he says. "We would have done better to get the customs officers drunk, but that would have taken twice as much alcohol."
"No, 10 times as much," protests Jérôme.
This season the Portes du Soleil piste map indicates day-long tours showing skiers how they can make the most of the astonishing 650km of runs connecting eight French and four Swiss villages. After doing one tour – spotting many of the 70-odd former customs outposts at the top of lifts – I'd explored the free-ride area above Plaine Dranse, where the resort encourages off-piste skiing because it controls the area for avalanches. I'd felt pretty pleased with myself for conquering the deep powder. However, in the museum I could only marvel at the exploits of Pierre Benand, who on skis would lower himself down and up the sheer cliffs on a rope, with a 30kg pack on his back.
In the days before ski lifts, skiers would attach skins to the bottom of their skis for the uphills to stop them sliding backwards. You can see originals at the museum. But to recreate the contrebandiers' adventure I attached modern-day synthetic "skins" to my skis, to attempt one of their favourite passes: the three-hour climb of the Col de Coux from Morzine.
The contrebandiers were generally better skiers than the customs officers, who initially were only kitted with snowshoes, and some did the descent from the Col de Coux so fast they were empty handed by the time the customs men caught up with them.
I took my time going down, carving graffiti-like squiggles in the deep powder this season has to offer. I arrived at the excellent restaurant of the Hotel Le National in Champéry, Switzerland, in time to meet my next contact, Fernand Rey-Bellet, 66, for dinner.
Coming from a Swiss family of contrebandiers, Fernand remembers being posted as a lookout as a boy, and recalls how his father was thrown into prison for giving clothing to some people who were lost in the mountains.
To some extent, he argues, the trade in goods was an extension of the natural hospitality that mountain people show in such a dangerous, yet beautiful, environment – particularly during the poverty-stricken war and post-war years when goods were in short supply.
However, it was in the early 1940s that the smuggling took on an altogether more urgent turn, when the cargo was often Jewish families looking for safe passage into Switzerland.
It was only in the late 1950s that smuggling began to tail off, as the post-war shortages abated and differences in taxation became less marked.
Jérôme also attributes the change to the prosperity that the arrival of winter sports brought. By the time he was on patrol he was mostly catching skiers with drugs on them. Switzerland has a liberal policy on cannabis compared with that of France. So does he miss the thrill of his old job?
Jérôme pauses for a while, before answering: "I think I miss the free ski pass most."
British Airways (0844 493 0787; ba.com), easyJet (0843 104 5000; easyjet.com), Jet2 (0871 226 1737; jet2.com), Thomas Cook (0844 879 8400; flythomascook.com) and Swiss (0845 601 0956; swiss.com) fly to Geneva from a range of UK airports.
Hôtel La Bergerie in Morzine (00 33 4 50 79 13 69; hotel-bergerie.com) has doubles from €188 per night, including breakfast.
Hôtel Le National in Champéry (00 41 24 479 11 30; lenational.ch) offers doubles from Sfr246 (£172), half board.
Hôtel Chalet d'Alizée in Châtel (00 33 4 50 73 00 53) has doubles from €112, half board.
The Vielle Douane museum (00 33 4 50 71 75 11; info.chatel.com) charges €4 for entry and is open from 2pm to 6pm except Saturday.
A six-day Portes du Soleil lift pass costs €225 (portesdusoleil.com).