On Saturday, the Kurdish-led administration said in an online statement that it had decided to submit detainees to its own "open, free and transparent trials" following the international community's lagging response.
The issue of foreign fighters is one of the most complex security and rights issues in Syria's 12-year war.
A Western diplomat working on Syria told Reuters the administration's decision was a surprise.
We take it very seriously that they are holding a lot of people – but this is a separate issue from trying them.
The diplomat said such trials would need particularly high levels of security and that the risk of a breakout by IS fighters would become higher.
Persons:
IS's, Badran Jia Kurd, Jia Kurd, Letta Tayler, It's, Orhan Qereman, Maya Gebeily, Frances Kerry
Organizations:
Islamic, Reuters, Human Rights, Thomson
Locations:
QAMISHLI, Syria, BEIRUT, Kurdish, U.S, Damascus, Canada, France, United Kingdom, Syrian, Qamishli, Beirut