The real outrage is the way European authorities are dealing with known returning Isis fighters.
I think you could make the case that anyone who left their country to help/support Isis is a war criminal and at very least an accessory too mass murder. But, beyond the legal niceties these jihadist should be incarcerated in some kind of Guantanamo like facility simply to protect the general public.
Yet virtually all the Western European countries are treating these jihadist killers as poor misguided misunderstood teenagers. The authorities are falling all over themselves to help them re-adjust to civilization.
they are loading them up with benefits, counselors and free housing.
When the inevitable terrorist assaults on their innocent civilians the authorities will ring there hands and pat each other on the back for trying to be understanding.