‘International law” has become a term commonly used by anti-Israel organizations. “In violation of international law” is what we hear in the media, in parliaments, and even in Israel’s Supreme Court. These words, which seem to require no further explanation or justification, have become employed to suggest, or downright assert, that the conduct of the IDF is illegal. But is this really the case? In recent weeks, the State of Israel has been facing a new threat, in the form of a massive mob marching from Gaza toward the border fences and attempting to cross them, with cries of hate and calls for murder emanating from loudspeakers used by the march’s organizer, Hamas. Terrorists trying to breach the fence with bombs and attempting to harm, destroy and murder are carrying out their attacks daily, using a variety of methods, including flammable kites.Hamas’s strategy, however, is not built on these terrorist tactics alone. Another, and perhaps even more significant aspect of the campaign is carried out in the public sphere and media by those that promote misinformation about Israel and its delegitimization around the world.In a manner that proved itself very effective for terrorist campaigns in the past, several radical organizations recently petitioned the Israeli High Court of Justice against the State of Israel and against the IDF’s protocols. Similar to the arguments made by various international voices on the events taking place on the Gaza border in recent weeks, “international law,” of course, was a significant part of their claims.Given that “international law” seems to be the current motto used by anti-Israeli organizations to attack the IDF’s conduct, let us examine together some of the principles of international law relevant to this context.Primarily, every country has the right to defend its borders and sovereignty. This is a fundamental principle of international law, anchored in the Charter of the United Nations and ratified by the International Court of Justice.Secondly, international law, indeed, makes a distinction between a combatant and a citizen and there are guidelines regarding what is permitted and what is forbidden regarding this distinction.International law recognizes situations in which a civilian may actively participate in combat and cases in which a civilian may assist combatant in a non-combat capacity.In 2010, the International Committee of the Red Cross (ICRC) published an “interpretive guidance of the notion of direct participation in hostilities under international humanitarian law” to mark this distinction. Undoubtedly, the petitioners in the above-mentioned case did not bother to study this guideline, chose to ignore it, or carried out a particularly far-reaching and unreasonable interpretative process in attempt to justify their arguments.The Red Cross guidance explains, for example, that in situations where the citizen directly participates in hostilities, it is possible by law to define the citizen as a combatant and to act against him using the same measures the law permits against combatants. In addition, the protection otherwise afforded to the citizen is also denied in cases where he or she chooses to partake in an activity the nature of which adversely affects the military operations or military capacity of a party to the conflict, by sabotage and other armed or unarmed activities.Numerous other examples presented by the International Committee of the Red Cross include unarmed activities restricting or disrupting forces deployment, logistics, information and communications technology (ICT), and even the removal of land mines placed by one of the parties.How do these rules apply in the situation before us? The actions of the IDF are carried out to stop the enemy’s actions as part of the armed conflict that Hamas is waging, in general, against the State of Israel, and it attempts to infiltrate Israel in recent weeks in particular.On the basis of the examples presented by the Red Cross, it is clear that Hamas’s activities, including the participation of Gaza civilians in march, are in complete violation of international law, consequentially denying both Hamas members and civilians involved in the hostilities any legal defense.It should be noted that the Open-Fire Regulations (in this context) refer to the penetration of forces into the “security obstacle space,” which is located only a few hundred meters from Israeli territory. The circumstances thus clearly indicate the security risk inherent in the presence of terrorist forces in this area, even more so in the case of large forces.In this context, the petitioners argue that international law prohibits the use of live ammunition against civilians.According to them, the crossing of the security fence does not in itself constitute participation in an act of hostility, if carried out by civilians.There is no need to be an expert on international law to see the obvious contradiction in every element of the petitioners’ arguments. In fact, the exact opposite is true: International law is very much aware of situations in which a person who is formally defined as a citizen participates in, contributes to and assists armed conflict, and allows, in a very broad manner, the removal of protections from the citizen in this context.A country is not required to hold off action until such civilians physically harm anyone before they can react and defend their territory, military forces and civilian population. On the contrary, a reaction meant to prevent such threats from coming to pass is perfectly legal.Here, we have a terrorist organization that organizes a mass march aiming to remove security barriers and enter the territory of a sovereign state, encouraging the masses to arm themselves and harm any Israeli in their path. There is no doubt that once those masses approach the fence and actively attempt to tear it down, the protection granted them by international law is no longer in effect.By virtue of this fact, the IDF has not only the legal and moral authority to thwart Hamas’s actions, but also the duty to do so.The Supreme Court, unanimously, agreed.The author is the director of the International Legal Forum and specializes in human rights and international law.