"The fact that Israel is the occupying power in the occupied territories carries with it tremendous legal and political significance, which of course is why Israel generally speaking denies that it is the occupying power or that the territories are occupied.
For a start, a very large body of international law prohibits settling or colonizing territories under occupation, as well as the acquisition of territory by war.
Most notably, Article 49 of the Fourth Geneva Convention prohibits occupying powers from transferring its civilian population into territories under occupation.
Supporters of the settlement movement sometimes try to get around this by arguing that it refers only to forced transfer of such populations.
Again, this is obviously specious since there are numerous other provisions of the Convention already prohibiting forced transfers of populations against their will, which would make Article 49 redundant and meaningless.
Moreover, the Geneva Convention was adopted in the aftermath of the second world war, and in full memory of colonization and population transfers engaged in by the axis powers, especially Nazi Germany, and this was clearly seen as a human rights abuse against people living under occupation.
This is why a prohibition of such activity was included in a human rights instrument designed to protect civilians in a time or context of war.
In other words, resting simply on the Geneva Convention, we can say with certainty that beyond simply being illegal, Israel's settlement activities are a human rights violation against the civilian Palestinian population in the occupied territories." Hussein Ibish