On a recent afternoon, Mahmoud Khalil sat in his Manhattan apartment, cradling his 10-week-old son as he thought back to the pre-dawn hours spent pacing a frigid immigration jail in Louisiana, awaiting news of the child’s birth in New York. “I cannot describe the pain of that night,” Khalil said finally, gazing down as the baby, Deen, cooed in his arms. Now, weeks after regaining his freedom, Khalil is seeking restitution.