New York's Democratic Socialist Mayor Zohran Mamdani’s push to determine whether city lawyers can act on the International Criminal Court’s warrant for Israeli Prime Minister Benjamin Netanyahu has turned a symbolic arrest question into a larger experiment: whether a mayor can use City Hall as a parallel arena for foreign policy. Mamdani, responding to questions about Netanyahu’s possible trip to New York for September’s United Nations General Assembly, said the Israeli leader “belongs in The Hague” and called him a “war criminal” over the ICC case. But the significance of a significant move extends beyond Netanyahu. Mamdani is repurposing the...