Congressional dominance theory holds that not only can the US Congress control the executive, it does. The terrorist attacks on New York and Washington on 11 September 2001 and the Bush administration’s ensuing global ‘war on terror’ suggest a different result. Bush’s response to 9/11 signalled not only new directions in US foreign and domestic policy but a new stage in the aggrandisement of presidential power in the United States and a further step in the marginalisation of the Congress. Informed by a constitutional doctrine unknown to the framers of the US Constitution, the Bush administration pursued a presidentialist or ‘ultra-separationist’ governing strategy that was disrespectful to the legislature’s intended role in the separated system. Using its unilateral powers, in public and in secret, claiming ‘inherent’ authority from the Constitution, and exploiting the public’s fear of a further terrorist attack and of endangering the lives of US troops abroad, the administration skilfully drove its legislation through the Congress. Occasionally, the Congress was able to extract concessions – notably in the immediate aftermath of 9/11, when partisan control of the government was split – but more typically, for most of the period, the Congress acquiesced to administration demands, albeit with the consolation of minor concessions. The administration not only dominated the lawmaking process, it also cowed legislators into legitimating often highly controversial (and sometimes illegal) administration-determined definitions of counter-terrorism and national security policy. Certainly, the Congress undertook a considerable amount of oversight during the period of the ‘war on terror’; lawmakers also complained. But the effects on policy were marginal. This finding held true for periods of Democratic as well as Republican majorities.