The ACLU said Tuesday that Zachary Fardon mounted a "blindside attack" on the deal.
Fardon resigned Monday after the Department of Justice asked 46 U.S. attorneys from President Barack Obama's presidency to resign.
Fardon also released an open letter citing many factors for the 762 homicides in Chicago last year. He suggested one was that officers now must spend 40 minutes to complete paperwork after each stop. He says "cops stopped making stops" and "kids started shooting more."
The ACLU says 40 minutes "wildly exaggerated." The group also contends not one arrest resulted from 700,000 such stops in 2014.