Wars are a tragic part of our history and they will surely be a tragic element of our future. After the creation of the United Nation, offensive wars have been outlawed and multilateral conventions refer to armed conflict instead of war. But wars of the future will not resemble our past wars. Flanked to the traditional warfare the cyber-war will be part of our future. We will fight our enemies remotely thanks to new weapons classes such as viruses or programmes that can harm our enemy operational capacity. The cyber-war is not covered in the existing law frameworks and the definition of the cyber-war is still highly debated. So, how can we react to a cyber-war if we can’t even agree on its meaning? One way to start would be picturing some situations where new international laws could be necessary. Imagine a new kind of assassin that can commit a crime without firing any shot nor being in the victim’s country. For example, a person working for the government uses a wireless device to send a signal to a foreign head of state’s pacemaker causing the disruption of the pacemaker and death of the foreign head of state. Would this cyber murder represent an act of war? As a second example, imagine a group of allied nations sneaking inside the informatics of a nuclear warship from an enemy country. This attack leads to the attack of a nuclear-aircraft carrier that was barely prevented from killing thousands of civilians. To defend itself, the enemy country responds by unleashing a defensive cyberattack that causes the breakdown of the power grids of allied nations. Hospitals can no longer treat patients, whole regions are without heating nor clean water, which, in the end, causes dozens thousands of civilian deaths. The origin of the power failure was the counterattack, but fragile infrastructure, weak cybersecurity, and the bad state of the electricity network, contributed to the death of civilians. Could the country fight back ? Who would it fight? And would his retaliation be considered an act of war? Do they constitute crimes of war against humanity? Who should be held responsible? The programmers who wrote the code? The military project manager who oversaw the creation of the code? The commander who pressed the button and triggered the event? The IT engineer who created the computers, knowing that they were intended to allow an attack? Because war is part of our universe for so long, we have laws to determine who should be held accountable for actions they took in combat. These legal frameworks aim at containing and at preventing atrocities from being even more atrocious. Commanding civilian aircrafts and using them as weapons, dropping atomic bombs, using gas chambers or poisonous gas in conflicts... All these actions, when they are committed, constitute acts of war and war crimes according to customary international law and the Hague Conventions. Again, the current legal framework remains silent on hypothetical questions and countless others because there is no easy answer. There are only two ways to make progress on these questions: peace or new laws. So what hypothetical, but plausible, scenario can you imagine in this context of cyber warfare ? How to design an international legal framework to prevent such activities?