Jews are an ethical group (Ashkenazi, Sephardic being the primary subsets). There is no such thing as a "legitimate claim." That's some Game of Thrones bullshit. They have a claim, backed by the United Nations .. and other nations with a lot of money and firearms.
In reality, for a claim to be "legitimate" ... well there is no legitimate. There is only what you can take and hold. The world backed Israel to take and hold a land and they did. The people on it didn't fight back hard enough or have enough resources and lost.
That's pretty much the entirely of how a nation is established and held. France back the colonies in the revolution, and that gave the colonies the ability to hold and form the States. Had they lost, they would have "legitimately" been a part of the British Empire for longer.
Trial by combat seems stupid if we applied it to a murder trial today. But trial by combat is exactly how nations are established. The most moral side rarely wins (see the DPRK, a.k.a North Korea or China/CCP). There is no legitimacy of case law when it comes to being able to create and hold a nation.