In general, taking territory from another country is treated under international law as illegal. Much of our sense that such illegality is as much morally wrong as it is legally prohibited comes from historical realities in modern history. The Nazi German takeovers of numerous countries across Europe between 1938 and 1945, together with the brutality with which they were carried out, stand even today as notorious examples of unacceptable behavior in an attempt to dominate other peoples without the least pretense of legality of purpose or practice.
Plans designed to bring about peace between the state of Israel and the Palestinians have been multiple, yet none has succeeded -- in all instances because of Palestinian rejectionism. The worst case was President Clinton's offer to the head of the PLO, Yasser Arafat, that would have required the Israelis to hand over about 90% of the lands to help create a State of Palestine. Arafat seemed to agree, then walked away and, from 2000-2005, waged against the people of Israel a campaign of terrorism known as the second intifada.
Most of the arguments concerning international law are based on a flimsy understanding of how and why Israel was brought into existence within international law, not to mention why Palestinian rejection has, for more than seventy years, been conducted outside that law. Moreover, in a clearer understanding, Israel's planned move appears to be legal.
The Israel-Palestinian conflict is unique for several reasons, and to proceed by citing legislation that applies to very different countries and historical situations pretty well guarantees discrimination against the state of Israel — a level of discrimination from which Israel has suffered from since the day of its birth.
There had never been anything resembling an Arab or Islamic state known as "Palestine". The name came from the ancient Romans' Latin version of the land for the Philistines and had nothing to do with Arabs or Muslims. At the time, the Roman Emperor Hadrian was trying to make it seem as if land actually named Judea was purely Roman and had nothing to do with Jews. The use of the word in Britain's 1922 Mandate for Palestine was simply based on the classical learning of the British learned and ruling classes.
Despite this, it is common today to find references to Palestine as a mainly Muslim Arab state that was supposedly "stolen" by Jews, or promised but not given to those people who describe themselves as Palestinians. That is an immense misconception, albeit one that seems to influence political and legal thinking internationally, especially among people who would like to believe it.
There are two chief inspirations for this mode of thinking. The first is Palestinian Arab nationalism, whose adherents portray Palestine as a long-term basis for loyalty from all the Arabs once living under the original Mandate territory or those currently restricted to Gaza and the West Bank. A state of Palestine is thought assured under the rights given to so many other people -- from the Irish to all other post-colonial nations achieved through the end of empires. But that argument does not validate the fantasy that any state of Palestine ever existed or that the Palestinian Arabs are the indigenous inhabitants of Israel, Jordan, and the would-be state of Palestine.
In fact, Palestinian nationalism as a political movement only started around 1920 and was formulated in the form of the Palestine Liberation Organization (PLO) in 1964.
As the PLO leader Zuheir Mohsen openly admitted in the Dutch newspaper Trouw in 1977: "The Palestinian people does not exist. The creation of a Palestinian state is only a means for continuing our struggle against the state of Israel for our Arab unity. In reality today there is no difference between Jordanians, Palestinians, Syrians and Lebanese. Only for political and tactical reasons do we speak today about the existence of a Palestinian people, since Arab national interests demand that we posit the existence of a distinct "Palestinian people" to oppose Zionism.
"For tactical reasons, Jordan, which is a sovereign state with defined borders, cannot raise claims to Haifa and Jaffa, while as a Palestinian, I can undoubtedly demand Haifa, Jaffa, Beer-Sheva and Jerusalem. However, the moment we reclaim our right to all of Palestine, we will not wait even a minute to unite Palestine and Jordan."
When international bodies legitimize Palestinian demands on the basis of such nationalism, they ignore the artificiality of the concept. To add to this is the manufactured and long perpetuated myth of the Palestinian refugees.