The pair had landed the aircraft at 4,450 metres before heading for the top of Mont Blanc, Europe's tallest peak.
French police spotted the plane on the east face of the mountain, Lt. Col. Stephane Bozon, who heads the gendarmerie's mountain rescue service in Chamonix, told AFP.
They intercepted the two Swiss mountaineers to get their identity and asked them to turn back. The pair were then allowed to take off, while the police figured out exactly what offense had been committed.
Law enforcement determined that article L363-1 of the Environmental Code does indeed prohibit aircraft from dropping off passengers in the mountain area for leisure activities, but no sanction is laid out for the violation of this provision, reports Le Parisien.
All that remains, then, is a prefectural decree from the 1960s laying out the landing rules in the area, the violation of which is punishable by a €38 fine.
Chamonix mayor Eric Fournier. Photo: AFP
Eric Fournier, mayor of the nearby Chamonix resort, called the incident a “provocation”.
“It constitutes an intolerable attack on the high mountain environment and on all existing protective measures,” Fournier said, describing the behaviour as “unprecedented”.
He has announced that he would be filing a complaint and has called for the regulations governing Mont Blanc to be updated.
The French Alps’ most famous summit is crawling with thousands of climbers during the summer months, aiming to reach the 4,809 metre summit.
Officials have been grappling with a surge in adventure-seeking tourists – some without sufficient equipment or experience – hoping to scale the mountain during the summer season.
The increase in numbers has led to some people camping illegally and concerns over sanitary risks such as water availability and problems with waste disposal.