“Based on the evidence before the Committee, it is clear that ATF agents in Phoenix and prosecutors in the Arizona U.S. Attorney’s Office embarked on a deliberate strategy not to arrest suspected straw purchasers while they attempted to make larger cases against higher-level targets. Although these officials claimed they had no probable cause to arrest any straw purchasers at the time, allowing hundreds of illegally purchased military-grade assault weapons to fall into the hands of violent drug cartels over the course of five years created an obvious and inexcusable threat to public safety on both sides of the border.