INTRODUCTION On Wednesday, October 27, 2010, a young woman dropped off two packages in San'a, Yemen-one at a UPS store, the other at a FedEx location. 1 Inside each of the two packages was a Hewlett-Packard desktop laser printer. 2 Yet these were no ordinary shipments of office supplies. Within the toner cartridge of each printer was a small amount of pentaerythritol tetranitrate (PETN), a powerful explosive material used in construction and industrial work. 3 The PETN had been inserted into the cartridges so that the printers, if X-rayed, would have appeared to contain ordinary laser printer ink powder. 4 The cartridges were wired to small detonators powered by cell phone batteries. 5 Both packages were addressed to synagogues in Chicago. 6 UPS and FedEx employees in Yemen screened the packages manually, saw nothing obviously amiss within them, and cleared the packages to be shipped to the United States. 7 The next day, intelligence officials in Saudi Arabia contacted their counterparts in the U.S. Central Intelligence Agency (CIA) to advise them that they had received a tip about two package bombs constructed by Al-Qaeda in the Arabian Peninsula (AQAP) that were en route to the United States-the same two package bombs that had been shipped from San'a. 8 Saudi officials were able to share with their American counterparts the precise tracking numbers for the packages. 9 A furious hunt for the packages began. Intelligence, law enforcement, and diplomatic agencies in the United States, United Kingdom, Saudi Arabia, Yemen, United Arab Emirates, and Germany, together with officials from UPS and FedEx, exchanged information and coordinated their responses to the Saudi intelligence tip, ultimately leading to the discovery of the package bombs. Local authorities disarmed the explosives at airports in East Midlands, England, and Dubai in the United Arab Emirates. 10 Investigators later determined that the bombs likely would have detonated in mid-flight, causing the airplanes carrying them to crash into the Atlantic Ocean. 11 The 2010 AQAP printer cartridge bomb plot was by any measure a serious threat to the global supply chain, particularly the U.S. air cargo system. The plot also illustrates a remarkable shift in our understanding of U.S. homeland security policy. Virtually every element in the plot, from the moment the package bombs were dropped off in Sana'a until the explosives within them were disarmed in England and the United Arab Emirates, took place outside the United States. The cooperation and coordination of multiple governments' security services and at least two air express carriers in the private sector led to the package bombs being located and disabled before the package bombs arrived in the United States.