Example: A column in the Los Angeles Times, December 11, 2009, by Eric Rosenman, titled A Right to Build. Rosenman points out (correctly IMHO) that the relevant League of Nations Mandate, allocating Israel as a homeland for the Jews, is still in effect. Under that Mandate, it would be perfectly legal for Israel to build settlements anywhere in the so-called West Bank -- perhaps even in what is now Jordan, since the original Mandate granted the whole of Palestine (now comprising Israel, the Palestinian territories, and Jordan) as a Jewish homeland.
But this analysis ignores the Oslo accords and other agreements between the government of Israel and the PLO/Palestinian Authority. Under those agreements, Israel ceded parts of what might otherwise be the Jewish Homeland to the Palestinians, in return for a cessation of hostilities.
While there have been numerous violations of that cessation, I think those treaties are still in effect unless/until publicly repudiated by Israel. And those treaties make the "West Bank" part of "Palestine". Israel has no business building "settlements" or any other use of the land for the benefit of Israelis on land that they have ceded to another country, even one like "Palestine" where the peace is uneasy at best.
Later on I'll attempt an ab initio analysis of the situation. It's not really all that complicated, even though I'm by no means a scholar of the history of the region.