The United States faces four immediate and potentially catastrophic threats. First, there is the threat of terrorist attack using a weapon of mass destruction (WMD) – a chemical, biological, radiological, or nuclear device. Second, in defending against this WMD threat, the United States may take measures that degrade the quality of our democracy and do so permanently, because the threat from catastrophic terrorism is indefinite. Third, we may not agree as a society on the nature of the threat and therefore on the nature of the response. In failing to agree, we may compromise. If we split the difference, we may fail to fully protect against a WMD attack or to preserve those values that underpin both our security and our liberty. Fourth, in addressing the threat of a WMD attack, and perhaps in coping with the war in Iraq and its consequences, we run the risk that we will degrade our ability to address this century's other certain threats – nuclear proliferation, instability in the Middle East, pandemic disease, environmental degradation, and energy and economic rivalry. This may occur because we are distracted or divided, or because we are exhausted.

National security law, by which I mean the substance, process, and practice of law, is central to addressing each of these threats. First, the tools necessary to provide physical security are defined in law, as is the process of decision-making for using them. Second, law is itself a national security tool.