As usual I suspect it all comes down to oil. In 2000, oil was discovered off the shore of Gaza. However, Israel has blocked efforts to extract the oil, stating that the profits would only fund terrorism.
In 2013 An Israeli oil well has been reported to contain a much larger reserve than originally estimated. The oil exploration company, Givat Olam, has now increased its estimate to 3.53 billion barrels of oil and has already sold $40 million worth of oil from the site.
While Israel is now facing a bright future as an oil producer, there is one problem: Meged 5 is located on the Green Line, the official border between Israel and Palestine. Lying a few dozen meters inside Palestinian territory, according to international law and the Oslo Accords, the well should belong to Palestine.
In answer to this problem, Israel has adjusted the path of its separation barrier, bringing Meged 5 onto its side of the wall. While the well is now under de facto Israeli control although most of the reserves lie under Palestinian territory.
Most of the above is copy and paste but should Israel be allowed to move it's borders, just like that, to take advantage of what appears to be Palestinian oil.
More here:
http://www.globalresearch.ca/oil-found-by-israel-should-belong-to-palestine-3-5-billion-barrels-of-oil-reserves-on-the-border-between-israel-and-palestine/5362043