Although the Law of Belligerent Occupation does not provide an explicit answer, the accepted approach is a “mirror image” of the conditions for its creation, that is, when the occupation army doesn’t maintain effective control in the territory, but instead, there is a new regime that has control. Occupation may end with an agreement, or when the occupant is forced out, but also because of a unilateral act. Israel withdrew totally from Gaza in 2005.
Does Israel have an “effective control” over the Gaza Strip? If we review the ruling of the International Court of Justice in the case of Congo vs. Uganda, that is, when an occupation means to effectively exert authority over the territory, then Israel is not (not even remotely) an occupant of the Gaza Strip.
The basic formula to define an “occupation” is stated in Article 42 of the Convention of The Hague on the Laws and Customs of War on Land (1907) that states: “Territory is considered occupied when it is actually placed under the authority of the hostile army. The occupation extends only to the territory where such authority has been established and can be exercised”.
The International Court of Justice (ICJ) states that there is a belligerent occupation when the occupying army actually exerts its authority over the territory, and in that way, supersedes the authority of the sovereign government in that area.
Some authors that are not very literate on legal topics argue that “if Israel withdrew unilaterally” it is guilty of not negotiating with the Palestinians of the Second Intifada, but if it “withdraws and there are no Israelis left in Gaza” then they’ll say that they still “occupy” it. This way, they live with their materialistic prejudgments that it is all about “occupation”.