From Fox News:

Jim Fox, the leader of the Mid-Iowa Boy Scout Troop 111, said the incident occurred earlier this month at a checkpoint along the Alaska – Canada border. The scouts and their leaders were on a 21-day trek from Iowa to Alaska – a trip that had been three years in the planning.

As their vans were moving through a checkpoint into the United States, one of the scouts snapped a photograph. Agents stopped the van and ordered all the passengers to get out. They told the underage photographer that he had committed a federal crime. It was unclear which agency with the Department of Homeland Security’s CBP agency was involved in the incident.