Jabhat al-Nusra and its affiliates should be prosecuted by national authorities not only for terrorist offences but also for war crimes, crimes against humanity and the crime of genocide, which are considered as “core international crimes”.
“ISIS has fulfilled criteria according to International Humanitarian Law as a party to a non- international armed conflict in Iraq and Syria acting as an organised non-state armed group,” reads the report.
https://www.neweurope.eu/article/eu-agency-says-isis-returnees-should-be-charged-with-war-crimes/