Two French girls, aged 15 and 17, have been captured by a security net that authorities are using to ferret out citizens who are considering travelling to other countries to join jihads.
The action is one example of how France is taking judicial action against citizens suspected of seeking careers as foreign fighters, even if they have yet to leave French soil. Thousands of European citizens have made the trip to Syrian battlegrounds, but there is no unified plan of action in Europe.
France is leading the way in Europe in the battle against this problem, and its sweep could get even wider with a planned law that would allow passports to be confiscated from those suspected of planning to fight in Syria or Iraq, and would create new measures to prosecute jihadi wannabes or returnees. France also is planning to join other European countries in blocking internet sites that espouse the jihadi cause.
All of Europe is worried about the return of battle-hardened citizens looking to continue their jihad in their homeland.
The concern has grown acute with the beheading of American journalist James Foley - by an executioner with an English accent. The group calling itself the Islamic State - now regarded by Western authorities as the most brutal among jihadi organisations - claimed responsibility this week by posting a video of the slaying on the internet.
France also points to the suspected killer of four people at the Jewish Museum in Brussels in May, Frenchman Mehdi Nemmouche, who fought in Syria, as evidence of the need to prevent potential catastrophes.
"Must I wait for a new Mehdi Nemmouche to fire before I act?" Interior Minister Bernard Cazeneuve said in a recent interview with the online publication Mediapart. He was referring to the tough new measures to be debated this spring (NZT) - and contending they will not compromise civil liberties.
France, with a Muslim population estimated at 5 million - the largest in Western Europe - is particularly concerned about the flight of youths to the battlefields.
French authorities say there are some 900 people from France who have been implicated in jihad - meaning they have taken part in one, plan to join one, or are returning from one. Several dozen have been killed.
Such measures would put France ahead of other countries in its effort to stop the problem, which some experts see as getting worse.
"It is impossible to quantify the risk of terrorist attacks by returning foreign fighters," Nigel Inkster, a former counterterrorism chief for Britain's M16 spy agency, wrote on his blog for the International Institute of Strategic Studies.
But he said those returning from Syria and Iraq "are likely to be better trained and motivated and more battle-hardened" than those who trained in Pakistan's tribal areas over the past decade.
Britain has struggled to deal with home-grown jihadi fighters since four British men inspired by al-Qaeda blew themselves up on the London transit system in 2005, killing 52 people.
An estimated 400-500 Britons have fought in Syria, scores of whom have returned home. Police have arrested 69 people this year regarding suspected Syria-related terrorist offenses, compared to 25 in all of 2013.
Britain emphasises a soft approach to routing out would-be jihadi or those returning from such conflicts. Its Prevent programme highlights outreach and aims to get institutions such as prisons, a known breeding ground for radicalization, and universities to watch for people at risk.
Germany also emphasises outreach. It has about 400 citizens who have become jihadi fighters in Syria and elsewhere, a third of whom have returned. School counselling, emergency hotlines and programmes to help find jobs for returning jihadi fighters are used.
Returnees are kept under observation, but can only be charged if there is proof they joined a terror organisation.
In Belgium, some are calling for a "homeland security office," but the current caretaker government has been unable to tackle the terrorism issue. Belgium, with a population of 11 million, has between 76 and 298 jihadi, according to a study by the International Center for the Study of Radicalization.
Further north, about 300 people from Sweden, Denmark and Norway have traveled to Syria - most believed to have joined the Islamic State group.
Could Foley's grisly public murder become a deterrent to would-be jihadi? Some think not. It is not the first time beheadings have been made available to the world via internet.
The ISIS pronouncement in June of a self-styled caliphate straddling the border of Iraq and Syria has energised some wannabe jihadi, according to Peter Neumann, a King's College London professor and director of the International Centre for the Study of Radicalization.
"They are saying, 'Maybe this is ugly, but there is a bigger cause that needs to be kept in mind, the creation of the caliphate. ... This is the price you have to pay for a really historical project,'" Neumann said.
The unidentified French teenage suspects, one from Tarbes in the southwest of France, the other from Lyon, allegedly acted together. They're neither the first adolescents nor the first females arrested in France. Some after returning from Syria or fetched by families at the Turkish border.
The girls are among some 60 people being investigated in France for criminal association in relation with a terrorist enterprise.