For decades, crimes contributed to an explosion in the size of the federal prison system, far outpacing any other charges brought by prosecutors. Now, just as the federal government has pulled back the throttle on the war, it is embarking on an unprecedented campaign to criminally prosecute undocumented immigrants crossing the border. The result: A new wave of non-violent offenders are flooding the nation’s prisons. "This is the crime du jour," said Judith Greene, director of the nonprofit Justice Strategies, which has focused on the private prison industry’s growing reliance on incarcerating undocumented immigrants. "It’s the war all over again. It’s what’s driving the market in federal prisons."