It was March 1968. Yaakov Herzog, director-general of the Prime Minister's Office, received a memo marked "Top Secret" from the Foreign Ministry’s legal adviser, Theodor Meron. As the government's authority on international law, Meron was responding to questions put to him about the legality of demolishing the homes of terror suspects in East Jerusalem and the West Bank and of deporting residents on security grounds.

His answer: Both measures violated the 1949 Fourth Geneva Convention on the protection of civilians in war. The government's justifications of the measures – that they were permitted under British emergency regulations still in force, or that the West Bank wasn't occupied territory – might have value for hasbara, public diplomacy, but were legally unconvincing.

The legal adviser's stance in 1968 is important today precisely because it is unexceptional. It's the view of nearly all scholars of international law, including prominent Israeli experts. The memo shows that from the very start of the occupation, central figures in the Israeli government knew that deportations and demolitions violated Israel's international commitments, and not just in the eyes of outside critics.

Yet both measures have been used ever since. If any later Israeli leaders saw Meron's opinion, they ignored it, and so misled the public and Israel's supporters abroad about the legality of their policies. If later leaders did not see the document, they nonetheless engaged in deliberate naivete, convincing themselves of the hasbara line in the face of the evidence.

Meron's memo was discovered in Yaakov Herzog's office files in the State Archives by Akevot, a new organization that has taken on the important task of searching archives for material shedding light on human rights issues in the Israeli-Palestinian conflict. (Herzog, by the way, was the uncle of the current Zionist Union leader, Isaac Herzog.) Last week, it made the document public. (You can see the original Hebrew document here; English translation here.)

The memo is not the first evidence of Meron's warnings, though. In 2006, I published another of his legal opinions, which I found in the late Prime Minister Levi Eshkol's declassified office files. Written in mid-September of 1967, about three months after the Six-Day War, it responds to a query from Eshkol's bureau about the legality of establishing settlements in the West Bank and Golan Heights.

He answered, "My conclusion is that civilian settlement in the administered territories contravenes explicit provisions of the Fourth Geneva Convention."

Central figures in Israel’s government at the time – Eshkol, Foreign Minister Abba Eban, Defense Minister Moshe Dayan and Justice Minister Yaakov Shimshon Shapira – all received that legal advice. A week and a half later, the cabinet approved settlement in the West Bank for the first time. Ex post facto, a few scholars have manufactured the justifications for settlement that are regularly cited for hasbara purposes. But their legal gymnastics have never convinced anyone who was not trying hard to be convinced.

About Theodor Meron: Born in Poland, he spent his early teens in a Nazi labor camp. After he arrived in Palestine, he made up for his lost school years, then completed a law degree at Hebrew University, a doctorate at Harvard and a fellowship at Cambridge, both in international law.

Then he joined Israel's foreign service. A decade after writing the legal opinions described here, he returned to academia to teach international law at New York University. In 2001, as a U.S. citizen, he was appointed a judge on the International Criminal Tribunal for the former Yugoslavia. Today he is president of that court and one of the world's leading authorities on humanitarian law in war.

After his 1967 opinion on settlement became public, he told The Independent that he "would have given the same opinion today." The reason is clear from his 1968 opinion on demolitions, in which he dismissed "narrow, literal" interpretations of the Geneva Convention. The convention, he said, "is a humanitarian convention that aims to protect the rights of a civilian population."

Put differently, the convention can't be interpreted by splitting hairs and forgetting real human beings. Its point isn't to protect states. It is to protect people from a state whose army has conquered the land where they live and before whose power they are otherwise defenseless. If it is ignored, their basic rights will be trampled.

The discovery of Meron's memo on demolitions and deportations is additional evidence that the regime under which the West Bank is governed began in deception and has been maintained by self-deception – by the government, by the hasbara machine and sometimes by our Supreme Court.

That memo has already been submitted to Israel’s High Court of Justice by the Center for the Defence of the Individual and other human rights groups, in support of their request that an expanded panel of justices hear their challenge to the policy of demolitions. The court should accept that request, which gives it a chance to end the deception and put a stop to an unjust policy – one that should have ceased the day the memo reached the Prime Minister's Office 37 years ago.

Gershom Gorenberg is the author of "The Unmaking of Israel" and "The Accidental Empire: Israel and the Birth of the Settlements, 1967-1977." Follow him on Twitter: @GershomG.