Well intentioned folks (and also some not so well intentioned ones) have been telling us for years, indeed decades, that internationally recognized borders between nations must be respected at all costs, and in cases of differences of opinion about them, old maps drawn by whomever are the only thing that count. Anything else would be unacceptable, and acquiring territory by violence would be the most unacceptable of all. Thus spake International Law.
This was always not convincing. First, because every border in human history drawn prior to a few decades ago was either created by God (see the borders of the UK, for example), or by men backed by the power to do the drawing. When you look at Israel's borders you'll find that respectable countries such as the US of A, the UK, and others, were still hatching plans to cede Israeli territory in the promotion of their interests, at least until late in the 1950s and probably all the way up to the Six Day War in 1967. (Michael Oren has some details in his excellent Six Days of War). The moment in time at which Israel's borders were sanctified and consecrated was the moment after they changed, and the old ones took on holiness to prevent the new ones ever being accepted.
Be that as it may, when it comes to the borders with Egypt, Lebanon, and Jordan, the lines drawn by some English sahibs in 1906 or 1918 or 1920 are generally regarded as sacred, and in each case Israel has been required to respect them down to the last inch (see: Taba) so as to have peace (or, in the case of Lebanon, so as not to have peace). The lines with the Palestinians that are regarded as sacred are the armistice lines of 1949; this is the line Israel accepts with Gaza, and doesn't accept on the West Bank. This non-acceptance generates endless opprobrium from most of the so-called "International Community", though in recent years some American presidents such as Bill Clinton and his successor have stated that perhaps some other line, should both sides agree, might also be acceptable if only agreement could be reached. The folks over at the Geneva Accord, by the way, also accept this. (Some prominent Palestinians among them, and no Likudniks).
And then there are the Syrians. They don't accept the internationally sanctioned lines, nor the lines they themselves agreed to in Rhodes in 1949. The only line they're willing to accept is the one they held on June 4th 1967, after they had used post-armistice force to take territory from Israel. Shlomo Avineri has a short but excellent article outlining the issues. Syria can't accept a line drawn by imperialist Europeans after WW1, only a line drawn by its own military; it can't even compromise for peace. And the entire concept of Lebanon is likewise unacceptable, since Lebanon was invented by the French.
The implication for Israel is that borders are determined by European imperialists when that's convenient for Egypt Jordan and Lebanon, by the 1949 armistice lines when that's convenient for the Palestinians, and by the force of arms and violence when that's convenient for the Syrians. I'm not necessarily saying these lines shouldn't be acceptable, but let's be clear about the total lack of consistency of it all.