A few years ago, there was another "march" on Israel. At the time, legal scholar Eugene Kontorovich wrote
a relevant article on the legality of Israel defending itself in such a situation - using a startlingly similar event that happened in the Western Sahara:
In 1975, Spain appeared ready to pull out of much or all of Western Sahara, a large desert region between Mauritania and Morocco. Rabat hoped to annex the mineral-rich territory, but its claims of sovereignty were successively denied by a report of a U.N. fact-finding mission and an advisory opinion of the International Court of Justice, both of which favored self-determination for the region.
Morocco was not deterred. Right after being rebuffed by those international organs, it mounted the Green March — sending 350,000 unarmed Moroccans on a well-choreographed hike into Western Sahara. Spain was not willing to fight against such numbers, and evacuated the territory. The Moroccan military moved in, and the territory remains under Moroccan control to this day.
The press has taken to calling the Arabs marching across the Israeli frontier “protesters.” In fact, “protests” are contained within a country;the organized crossing of a frontier is an invasion. In 1975, when Western Sahara was the victim, the world community was clear on this point (even though the Moroccans were unarmed.). Other Arab leaders called the Green March “a violation of the sovereignty of” Western Sahara and “an act contrary to international law.” Prominent international scholars described it as an illegal use of force, a “stealing of the Sahara,” in the words of one of the leading international lawyers of the time. The U.N. Security Council passed a measure that “deplored” Morocco’s invasion.
Moreover, despite the nominally civilian character of the marchers, several U.N. General Assembly resolutions recognized that the enterprise constituted a military occupation by Morocco. Observers noted that the march could not have gone off without the permission, and indeed encouragement, of King Hassan of Morocco, and thus he must take responsibility as if he had ordered army units across the border. It was a conquest despite the lack of arms: A large organized mob can be as forceful as an armed military unit. Indeed, as the Spanish capitulation proved, a march could be a more effective tool of conquest than a military strike against Western armies reluctant to fire on civilians.
(full article online)
What are Israel's rights under international law to defend itself from Gaza "marchers"? ~ Elder Of Ziyon - Israel News