The bodies of Louisa Vesterager Jespersen, 24, from Denmark and Maren Ueland, 28, from Norway, were found on 17 December in an isolated area near Imlil, on the way to Mount Toubkal, North Africa's highest peak and a popular hiking destination.
More charges could follow, the prosecutors said.
A memorial to the two women in Copenhagen, Denmark.
Moroccan authorities have arrested about 20 people over their alleged links to the double murder, labelled a "terrorist" act by Rabat.
The statement said that the arrested man is suspected of being involved in providing training to other arrested people and engaging in the recruitment of Moroccan and sub-Saharan African citizens to terrorist organizations in Morocco.
The Swiss national also holds a Spanish passport and had Moroccan residency, the CBJI said. Earlier, the country's authorities detained 18 people in connection with the killings, including four suspects believed to be inspired by Islamic State (IS, formerly ISIS/ISIL).
Nineteen other men have been arrested in connection with the case, including four main suspects who had pledged allegiance to Islamic State in a video made three days before the tourists' remains were found.
One of them, a 25-year-old street vendor, is suspected by investigators of being the head of this "terrorist cell".
Danish and Norwegian leaders have both condemned the killings and Moroccan prime minister Saad Eddine El Othmani has described them as a "stab in the back of Morocco and Moroccans".
However, none of the four had contact with ISIL members in Syria or Iraq, he said.
However, it is no stranger to terrorism with major attacks in Casablanca (33 deaths in 2003) and Marrakech (17 deaths in 2011).