After 9/11, U.S. President George W. Bush announced his determination to do whatever was necessary to prevent future terrorist attacks against the United States. Following the lead of several countries that had recently come to similar conclusions after their own bitter experiences -- including India, Israel, Japan, Russia, Spain, and the United Kingdom -- the United States tightened its immigration laws; increased the protection of its borders, ports, and infrastructure; criminalized providing "material support" for terrorist groups; and tore down the wall between the intelligence agencies and law enforcement agencies, which had crippled counterterrorist efforts for decades. Washington did not authorize preventive detention, as other countries had, but it used other measures to hold persons against whom criminal charges could not be brought -- thereby preventing terrorist attacks. The U.S. government also led or joined various international efforts aimed at warding off new dangers, such as the Proliferation Security Initiative, through which over 70 states cooperate to interdict the movement of nuclear materials across international borders.
But the Bush administration's call for preventive action went further: it endorsed using force against states that supported terrorism or failed to prevent it. This was a particularly controversial position, since using (or threatening
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