Following the terrorist attacks on the United States on September 11, 2001, many industrial countries toughened their internal security measures. Yet as Sandler stresses, unilateral efforts, while important, may simply shift terrorist activity to countries that lack the capacity, resources, or political will for similar security upgrades. Control of terrorism through enhanced protection against attacks is a global public good of the weakest link type: “everyone’s participation is essential since the smallest provision level determines the amount of the public good that generates benefits” (Sandler, p. 199). Security in air travel or container shipping, for example, depends on adequate screening of cargo and passengers in every country. Once industrial countries have attained a certain level of national security, instead of spending more on upgrading national security, it can be in their self-interest to help poorer, weakest link countries contribute to global security—and to move the issue up to the international level for complementary collective action.