The whole world is talking about the victory of a people who faced annihilation by the Islamic State in October 2014. The starting point of the victory was when the United States-led coalition decided to act with the Syrian Kurds against IS in the last minutes of the fall of Kobani, a small town at the north of Syrian border. In other words, the most organized force among the non-state actors during the Syrian civil war changed the course of combat with technological equipment and air support.In a press release on March 17, US-led Syrian Democratic Forces (SDF) spokesman Kino Gabriel gave striking information about the SDF-led siege of the town of Baghouz, the last piece of land held by Islamic State. He said that 29,600 people, including an estimated 5,000 fighters, the majority of whom were with their families, had surrendered. Today, this trouble for mankind has been completely defeated.However, there are many crucial questions left regarding the mindset that ideologically underpinned IS. The most controversial question is, what will become of the foreign fighters who joined IS, and their families?This question was first addressed by French Justice Minister Nicole Belloubet in January 2018. French citizens who joined IS, she said, could be dealt with in courts in the self-declared Kurdish autonomous region.On February 17, 2019, US President Donald Trump called on European partners in the coalition against IS to take back foreign fighters who were their citizens and had joined IS. But paradoxically, a few days later, he rejected the demand to return Hoda Muthana to the US, an American citizen who joined IS.The final statement on this issue came from Swedish Prime Minister Stefan Löfven, who called for an international tribunal to bring IS fighters to justice. He described the actions of the IS terrorists as pure and ritual evil, and implicitly stressed that proceedings can be brought to the International Criminal Court (ICC) to prosecute them for war crimes.According to the territorial principle of public international law, any criminal offense committed within the borders of a sovereign state shall be dealt with by the legal bodies which are authorized within its borders. However, the existence of the ICC – which is established to prosecute individuals for crimes against humanity, war crimes and international crimes of genocide – must also be included.In June 2016, the United Nations Commission of Inquiry on Syria recognized the series of bloody massacres committed by IS against Yazidis as genocide. Since Syria is not a signatory to the Rome Statute of ICC, this might be handed by the United Nations Security Council to the ICC, as in the case of Darfur/Sudan.In order to understand the importance of the situation, we must return to the emergence of IS as a global phenomenon. Although many of us did not accept it, IS shaped itself as a universal organization and a very inclusive network. According to the National Bureau of Economic Research, as of December 2015, approximately 30,000 fighters from at least 85 countries had joined IS. It constructs its own ideological pursuits with both religious references and political claims.Erasing traces of the strong background of IS in the field is as critical as military victory. It is important to document its crimes against humanity and the testimonies of the suspects in order to not rebirth IS-like entities. It is very clear that if the rebuilding of Syria as a democratic government is not considered within a legal and social integrated project, we cannot talk about a sustainable peaceful environment in the short term for the Middle East.The trials in this case can become examples that show the possibility of justice in war crimes trials for the benefit of the shared memory of humanity. We will face the question about the perpetrators of the genocide that cannot be ignored: How do people who have “normal” relationships in their daily lives suddenly become part of a terrible process like the Islamic State?The writer is a student at the Center for Middle Eastern Studies at Lund University in Sweden.