When discussing whether Russia is occupying parts of Georgia in 2008, HRW writes:
Russia is bound by the law of occupation wherever it exercises effective control within the territory of Georgia without the consent of the Georgian state. Anywhere Georgian authorities are prevented from their full and free exercise of sovereignty - such as denying access for Georgian authorities including law enforcement and military forces - because of Russian presence, Russia is assuming the role of an occupying power for the purposes of international humanitarian law, and all its obligations towards the civilian population remain.The examples given in the first paragraph necessitate a presence of troops in the actual territory. The second paragraph, where such troops are not present, is ambiguous: HRW says accurately that there is a still an obligation for humanitarian access but it pointedly does not say that this is considered a legal occupation. The two issues are separate, as legal blockades (for example) must allow basic needs to get through but do no indicate an occupation.
If Russia exercises effective control of access to an area, such as a so-called buffer zone, even if it grants access to some authorities, for example, Georgian police, it is still bound by its obligations to the civilian population to ensure public safety and welfare and permit humanitarian access.
However, in regards to Gaza, HRW has been explicit that Israel remains an occupier since Israel first announced the disengagement:
“The removal of settlers and most military forces will not end Israel’s control over Gaza,” said Sarah Leah Whitson, Executive Director of Human Rights Watch’s Middle East and North Africa Division. “Israel plans to reconfigure its occupation of the territory, but it will remain an occupying power with responsibility for the welfare of the civilian population.Again, this is not a direct contradiction, but the first source (written in 2008, after HRW was already committed to the definition about Gaza written in 2004) does imply that "effective occupation" means troops on the ground.
“Under international law, the test for determining whether an occupation exists is effective control by a hostile army, not the positioning of troops,” Whitson said. “Whether the Israeli army is inside Gaza or redeployed around its periphery and restricting entrance and exit, it remains in control.”
However, the ICRC is also explicit in its definition of occupation - and proves that HRW is wrong.
The ICRC has a document that describes belligerent occupation, and it says clearly:
Occupation ceases when the occupying forces are driven out of or evacuate the territory.
It would be interesting to hear whether any HRW official or Amnesty, for that matter) could be quoted as saying that they disagree with the ICRC.
By the way, the US Army and Navy Field Manual 27-5, Section 1-1b, has its own definition of occupied territory that is also at odds with HRW:
The term “occupied territory” is used to mean any area in which military government is cxerciscd by an armed force. It does not include territory in which an armed force is located but has not assumed supreme authority.
There is one thread of consistency throughout this research: by any definition of occupation that pre-dates Israel's disengagement, there is no way that Israel is legally occupying Gaza. Apparently, some NGOs have felt it necessary to redefine a very specific legal term to apply to Israel ex post facto.
This, of course, calls into question the objectivity of these NGOs altogether.