Aren't they already in concentration camps? At least they are in Serbia. We haven't started exterminating them (yet). Would be easier than sending them back to Syria. Kinda impossible now, with Erdogan going full Idi Amin.
Edit: Easiest way is to go full Stalin. Disobedient in "worker" camps, to make example for others. Ban Islam in Europe. Problem solved.
But muh civil rights, personal freedom of expression? Can't have the cake and eat it. Native and foreigners are never treated equally.
It is better to deny certain rights to minority, but let them live normal life than to act like everything is okay but secretly pack them into mass graves, Milosevic style.