In early March, French officials successfully prevented two girls from leaving to join ISIS in Syria, and the country collectively breathed a sigh of relief. But what happens next? What happens to the kids who are saved from falling under the spell of ISIS’s suicidal and apocryphal ideology, but often against their will?

It may be too soon for studies to reveal whether would-be foreign fighters make the transition back to normal, productive lives. Nonetheless, programs being tested in different countries—and the anecdotal evidence beginning to trickle in—hints at less-than-stellar outcomes.

The most troubling results, of course, are represented by those individuals prevented from joining jihad in Syria who have gone on to carry out terrorist plots at home. Ibrahim Abdeslam is one such individual. Reportedly thwarted from traveling to Syria in early 2015, Abdeslam was intercepted by authorities in Turkey and forcibly returned to Brussels. In November 2015, Abdeslam, blew himself up outside Paris’s Comptoir Voltaire cafe as part of the deadly ISIS attacks, which killed 130 and wounded more than 350.

How did Abdeslam manage to participate in such a complicated and deadly assault after being stopped en route to Syria? Reports say that Abdeslam was interrogated by Belgian police upon his return, but was ultimately released after authorities concluded that he showed “no sign of a possible threat.” Part of the problem was a complicated legal situation. According to one unnamed Belgian authority, “We knew [Ibrahim and Saleh Abdeslam] were radicalized and could have visited Syria,” but Ibrahim could not be prosecuted because “we had no evidence that he participated in the activities of a terrorist group.”

Abdeslam is only one of many disappointed foreign fighters who have been quietly reintroduced into Western society. Whether or not a would-be foreign fighter will be monitored, arrested, prosecuted, or placed into a de-radicalization program is very much a case-by-case decision. What’s even less clear is the success rate of de-radicalization and other intervention programs.

Consider the case of “A,” a Jewish girl from Paris who was inspired to join ISIS. “A” was just moments away from boarding a plane to Syria when she was convinced to stay behind. Her parents remained vigilant, and “A” was enrolled in a de-radicalization program, the Centre de Prévention des Dérives Sectaires liées à l’Islam (Center for the Prevention of Sectarian Abuses linked to Islam). Nonetheless, the girl reportedly still managed to stay in touch with her ISIS recruiters, even after her travel plans came to an end and after she was ensconced in the de-radicalization program.

One of the two girls stopped in early March, Israé, had attended that same de-radicalization program, apparently to little effect. Two years after Israé’s first attempt to leave for Syria, and her enrollment in the program, Israé again tried to join ISIS.

Now, Israé and her cohort Louisa are again living at home, and both face travel bans. Still, reasonable concern exists regarding how their guardians will rehabilitate the two girls, and constructively redirect their pro-ISIS fervor. After all, although Israé, Louisa, and “A” ultimately were stopped before reaching ISIS-controlled territory and becoming jihadi brides, they have both shown a fierce determination to maintain their ties to the terrorist group.

Today, concerns exist over not only reintegration, but governments’ capacity to effectively monitor ongoing threats at home. In 2015, France’s resources were stretched exceptionally thin. Since then, increased funding has been devoted to domestic and international surveillance following passage of the country’s “Stop-Djihadisme” program. France has declared that a number of domestic terrorist threats have been thwarted, but massive intelligence gaps have been revealed following the Paris attacks in November.

Similar problems plagued Belgium long before terrorists targeted the Brussels airport and metro. The country is struggling to maintain surveillance on the hundreds of Belgians already abroad, as well as track suspected extremists at home.

ISIS hopefuls, their families, and their communities today remain vulnerable, not only due to resource limitations, but to a dearth of deradicalization programs whose effectiveness has been established. So what happens next? The reality is often a mosaic of hastily thrown together solutions, tailored for each individual, and occasionally misapplied.