In a stunning, generation-defining decision, Israel’s Supreme Court has unanimously ruled that people who became Jews through Conservative and Reform conversions must be considered as Jews for purposes of the country’s Law of Return, allowing them a fast-track to citizenship. Israel’s legislature, the Knesset, has the authority to reverse the decision and restrict the Law of Return to Orthodox converts. That may well happen — but if it does, it would represent a serious blow to relations between American Jews, most of whom are not Orthodox, and the state of Israel.

The Law of Return is foundational to Israel’s self-concept as a Jewish democratic state. It establishes the principle that Jews may become citizens of Israel simply by showing up in the country and declaring their intention to become citizens. As written, the law defines a Jew as "one who was born to a Jewish mother or converted, while not being a member of another religion.” The case before the Supreme Court involved the vexed question of the meaning of the word "converted:” Which conversions count as qualifying a person for citizenship under the law?

The answer has massive implications for the nature of Israeli identity. Israel’s large Orthodox population mostly would prefer that it be restricted to conversions performed by Orthodox rabbis.