Open this photo in gallery: Pro-Palestinian activists hold signs and wave flags as they participate in a Fight for our Rights rally in support of Mahmoud Khalil in New York's Times Square on March 15.LEONARDO MUNOZ/AFP/Getty Images Student journalists at Columbia University say the right to free expression is in doubt after the arrest and detention of student protester Mahmoud Khalil, a Palestinian with landed immigrant status, and the threats of deportation made against several others who were involved in the pro-Palestinian protests. Mr. Khalil, 30, had been an organizer and activist who participated in the encampment on the lawn...