State sponsorship of terrorism is a complex problem that cannot easily be solved. Despite diplomatic protests, economic sanctions, and even military pressure Iran, Pakistan, and Syria have supported numerous terrorist groups for decades. The Taliban persisted in its support of al-Qa'ida until US-backed forces toppled it from power. Many other states also backed terrorist groups, at times even risking war to do so. Such persistence in the face of pressure suggests that cutting the deadly connection between states and terrorist groups is difficult at best and impossible at worst. Yet the picture is not entirely bleak. Although there are no perfect solutions, careful policymakers can design better ones and avoid many common mistakes that can make the problem of state sponsorship worse.

States seeking to halt support for terrorism generally use several methods, almost always in combination. They include engaging the state sponsor; using massive military force to change a regime; punitive or coercive uses of military force; threats of military force; varying levels of unilateral and multilateral economic sanctions; backing an insurgency or terrorist group of one's own; and diplomatic isolation. Each of these tools has different benefits, costs, and conditions under which they are effective. All, however, can backfire and actually strengthen the bond between a terrorist group and its supporters.

Because states back terrorists for reasons ranging from a shared ideology to ruthless realpolitik, there is no universal policy or simple response that the United States or other concerned countries can take to get state sponsors out of the terrorism business.