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Well, it is their law, longstanding. Jordan too. But when an American citizen is sentenced to life in prison for selling real estate to a Jew, offensive to most but not all Americans, it is a legitimate issue for our government to address. At whatever time or in whatever way the government considers appropriate. Plenty of people on the left sympathize, though I doubt many if any will publicly.
If that land is in Israel, the Israeli government owns all land - there is no private ownership. You pay rent for the land. That is what we were told at while asking question at the American Embassy Tel Aviv in 2006.