I'll try to summarize:
IfNotNow's example questions are:
The definition of “occupation” comes from Hague Convention of 1907:
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 Fourth Geneva Conventions do not define “occupation” but set up rules to protect civilians under occupation.
Israel's position is that the land isn’t “occupied” but “disputed." The reason it isn’t occupied is that it had no recognized sovereign before 1967, as Jordan’s annexation of Judea and Samaria was not recognized by most nations.
The Hague definition only applies to parties of the Convention, meaning states.
Hans Kelsen wrote in Principles of International Law in 1952 (before international law was twisted specifically to attack Israel:)
If the territory is not to be considered a stateless territory, it must be considered to be under the sovereignty of the occupant belligerent, which—in such a case—ceases to be restricted by the rules concerning belligerent occupation.
“The Mandatory shall be responsible for placing the country under such political, administrative and economic conditions as will secure the establishment of the Jewish national home….”
The League of Nations decisions remain legal under the UN. Since Jordan’s claim from 1949-1967 was illegal, the only valid claim on the land is that of the Jews under the terms of the League of Nations.
Now, this might seem like a cop-out. The Geneva Conventions describes how to treat civilians humanely under occupation, and saying that the areas aren't occupied in a strictly legal sense should not give Israel carte blanche to treat Palestinian Arabs badly.
But Israel has voluntarily enforced the Geneva Convention humanitarian rules in the territories, but never accepted the idea that they are legally occupied – it always maintained they were disputed. This is why Israel feels that building Jewish communities in the territories is legal - with the exception of Hebron, where Jews lived continuously before 1929, all Jewish settlements are in areas that Arabs didn't live, on public lands (sometimes mistakes are made and either those buildings are demolished or the Arabs are compensated, based on Israeli Supreme Court rulings.)
By the way, no one who is serious accuses Israel's Supreme Court of ignoring international law. Their opinions are sober, detailed and publicly available. I have yet to see anyone show how their opinions that allow Israel to act in the territories are in violation of international law.
Beyond these points, parts of the territories aren't occupied for a completely different reason.
In an occupation, the hostile army has complete control over the territory - it is required to set up court systems and enforce existing laws.
By Geneva’s definition: [T]he Occupying Power shall be bound, for the duration of the occupation, to the extent that such Power exercises the functions of government in such territory
By the Hague’s definition, it requires “boots on the ground”
Gaza is certainly not occupied now since there is not a single Israeli soldier there. Neither is Area A, since the PA has military control over those areas. Israel is not acting and cannot act as the government in those areas.
(People who say that controlling the borders is “occupation” have zero legal basis for their opinion.)
IfNotNow asks about the effect of the Israeli presence in the territories on Palestinian (and Israeli) lives. They only care about Palestinian human rights - but they ignore Israeli human rights.
Before the first intifada, there were no (or few?) checkpoints. Palestinian Arabs and Israeli Jews were able to simply drive all over Israel and the territories with few restrictions. I once spoke to someone who used to Israeli kosher challah bread in Ramallah, imported Friday mornings to allow settlers to not have to drive to Jerusalem.
All of that changed because of the first and second intifadas, the waves of Arab terror and suicide bombings and bus bombings from 1988, through the 1990s when there were many terror attacks during the Oslo peace process, and then the major wave of terror that happened after the Palestinians rejected two serious peace offers in 2000 and 2001, pushed by Bill Clinton.
All restrictions on Palestinian mobility is a direct result of terror. Israel isn't trying to restrict anyone's human rights, but Israel's main job as a sovereign nation is to protect its citizens. The rights of Israelis to live without being blown up are certainly more important than the rights of Palestinian Arabs not to wait for minutes at checkpoints to ensure they aren't bringing bombs or guns.
No one talks about Israeli human rights. But human rights are human rights to all, and Israel has to find a balance that allows the maximum of human rights for Palestinians without compromising in the security of Israelis. The line is fine, and it moves, based on Palestinian Arab actions.
The Oslo peace process is now 25 years old. Palestinian Arabs have had 25 years to teach an entire generation to live in peace with Israel, and they have done the opposite. Terrorists are heroes, and they and their families are paid salaries by the PLO. Not all Palestinians are terrorists, but polls show that after major terror attacks on Israeli civilians, a vast majority support those attacks. And polls have also consistently shown that even the Palestinians who say they support a two state solution only look at that as a stage before taking over all of Israel. This is the major reason there is no peace today.
Every Israeli government, including the current one, wants to live side by side in peace and security with a Palestinian state (or entity, if you will) that doesn't threaten Israel. No one wants to control millions of potentially hostile people. But right now that is impossible - a hostile independent Palestine in the territories could easily acquire shoulder mounted missiles to threaten all Israeli air traffic, for example. This is not acceptable to any nation.
So the current situation, as bad as it is for Palestinian Arabs, is the least bad situation if you value Israeli lives as well. And when the PA does take security seriously, restrictions on Palestinians are lifted (there used to be far more checkpoints than today.)
IfNotNow hates it when Zionists say "it's complicated." That's because they are invested in a simplistic viewpoint where Israelis are evil and Palestinians are good. That is highly inaccurate, borderline racist and betrays an agenda where Israeli lives are worthless. If Birthright participants want to know the facts, they need to invest the time into understanding both sides of the story.
And Birthright guides must be more than tour guides. Understanding Israeli and Jewish history is not enough preparation to handle loaded questions that presuppose the answers. They need to understand the talking points of Israel's enemies like IfNotNow and know how to counter those arguments.
I'm willing to help.