The Balfour Declaration didn't legally mean much until it was supported by the international community

Today is the anniversary of the Balfour Declaration, where Great Britain announced its support for the establishment of a "national home for the Jewish people" in Palestine.

As with every year, the Palestinians are marking the day with mourning. PA president Abbas instructed all flags to be flown at half-mast every November 2. Palestinians got the secretary general of the Arab League to issue his annual statement calling on Great Britain to "correct this historical mistake and assume its historical, legal and moral responsibility by offering an apology to the Palestinian people and recognizing the Palestinian state on the June 4, 1967 lines with its capital East Jerusalem."

They like to pretend that the Balfour Declaration is the source of their problems. 

But it was just a letter. It wasn't a legal obligation. 

What happened afterwards is arguably more important.

It was endorsed by the French and Italian governments, as well as the United States. It was incorporated into the San Remo Resolution in 1920. Finally, it was then incorporated into the Mandate for Palestine by the League of Nations.

That's when it became international law to support Palestine as a national home for the Jewish people.

Interestingly, the Arab opposition to the Mandate was not only against the concept of a Jewish homeland, but also  against the concept that Palestine was a political entity of its own rather than part of Syria. (Of course, they also insisted that Jewish immigration be stopped totally.) 

There were years of work by Zionists to turn Balfour from a vague statement of intent into international law. That is part of what gives Israel its legitimacy under international law today.

When the Palestinians say they want to reverse Balfour, they are saying they want to erase Israel. 

The Mandate's incorporation of Balfour is also the source of Israel's legal claims to the entire area under the British mandate. Nothing that happened since then has superseded the Jewish national claim to Judea and Samaria.  

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