Your appeal to authority does not matter as this is a matter that was not never resolved in courts, and the reasons Israel has withdrawn in the first place was due to international support, which also included the western countries you mention.
Generally, Anyone who can read the definition of occupation in both international law and English knows it will be very hard to prove what went in Gaza previous to the war was occupation.
The fact that this, similar to other axioms in the conflict are considered truism while no one stops to thinks on whether they even make sense, is a good example of prejudices at play.
Another recent example, the UN having to redefine famine in order to declare famine in Gaza. Do you see the pattern?