"There is no perfect answer to this question," says Sofia Koller, a senior research analyst at the Berlin office of the Counter Extremism Project, or CEP, who's written several reports on the topic. "Politically it [repatriation] is controversial but from many other perspectives, it's not at all. Especially if we consider what the negative outcomes of not repatriating might be — that is, the kinds of outcomes we're seeing at the moment."