Open this photo in gallery: Signs in support of detained graduate student Mahmoud Khalil are readied during the nationwide Hands Off! protest against President Donald Trump and his advisor, Tesla CEO Elon Musk, in Washington, on April 5.AMID FARAHI/AFP/Getty Images Mahmoud Khalil, a graduate student in the international affairs program at Columbia University and an important organizer of the pro-Palestinian demonstrations on the Manhattan campus last year, was arrested by U.S. Immigration and Customs Enforcement (ICE) last month. The White House later confirmed that his detention was justified by President Donald Trump’s executive order combatting antisemitism, which authorizes the administration...