New York City Mayor Zohran Mamdani said Palestinian activist Mahmoud Khalil “must remain free,” in a social media post shortly after a federal appeals panel reversed a lower court decision that released the former Columbia University graduate student from an immigration jail. Khalil, a lawful permanent resident, was arrested at a Columbia University-owned residence last March, related to his participation in a Gaza solidarity encampment organized by students in 2024. He was held for about three