Professor Eugene Kontorovich has a controversial op/ed in the New York Sun explaining why the latest proposals for a ceasefire between Israel and Hezbollah violate international law. He writes:
The most surprising aspect of international proposals for a ceasefire
in the Israel-Lebanon conflict is their endorsement of Hezbollah's
demand that Israel give it territory, known as the Sheba Farms, in
exchange for a end to rocket attacks on Israeli cities...What is
certain — and yet entirely neglected in the discussion of the issue —
is that the proposal violates bedrock norms of international law. Nations cannot enlarge their borders through the use of aggressive
force. There are no exceptions to this non-acquisition principle.
Let's leave to one side the wisdom of ceding territory to a terrorist organization like Hezbollah and deal instead with Kontorovich's seductive claim that it violates international law.
It is certainly true that the UN Charter permits no exceptions to the non-acquisitive principle (this is the practical effect of Article 2(4) and Article 51 of the Charter). Still, Kontorovich is overstating his case with regard to international law generally - unless, that is, he is laboring under the mistaken view that international law is whatever the United Nations and Kofi Annan say it is. It isn't, mercifully.
The truth is, although there is a general presumption against the acquisition of territory as a result of aggression, this is a neoteric doctrine - emerging as it did in the 20th century. In the past, conquest was a legitimate way to acquire territory. Of course, during the 20th century we have understandably moved away from this extreme position, but there is no absolute rule of non-acquisition when aggression is involved.
For example, the rule of uti possidetis - the principle that territory vests to the victorious party - has essentially kept the fragile peace in many African conflicts after initial disputes over post-colonial border. The International Court of Justice recognized something approaching this in its deliberations on the land and maritime border dispute between Nigeria and Cameroon. Recently, this led to a truce and subsequently an agreement between these two countries. International law is better discerned from the way states act and their reasons for so acting rather than universalist-abstractions in the UN Charter.
In many ways, Kontorovich reveals the poverty of international law as a dispute resolution mechanism. Its boundaries are unclear, far too many people make authoritative statements when nuanced ones would be more appropriate, and by focusing too much on ex ante rules, it does not concern itself with creating lasting peace.
So, to answer the question posed in the title - International law isn't standing in the way of a ceasefire, the UN Charter is.