16 Melbourne University Law Review [Vol 41(2):Adv the powers was triggered by a difference in political perspectives and priorities between the Cameron government and the prior Blair and Brown governments. The idea that broad use of citizenship stripping powers has not been critical to ensuring national security in the UK could, in part, be explained by the fact that, since 2002, the UK has enacted a wide range of other national security measures of greater utility.68 Indeed, a number of other more targeted measures serve similar objectives to citizenship stripping, such as those for the detention and removal from the UK of persons deemed to pose a security risk, and the prevention of their re-entry. Initially, such exclusionary mechanisms were directed towards non-citizens resident in the UK. However, they have increasingly included citizens within their scope. For instance, the Home Secretary enjoys under the royal prerogative an executive discretion to withdraw or refuse passports.69 Historically, these powers are thought to have been used very sparingly.70 However, in April 2013, the criteria for using the prerogative were updated.71 Between the update and November 2014, the Home Secretary invoked the passport refusal and cancellation powers 29 times to ‘disrupt the travel of people planning to engage in terrorist-related activity overseas’.72 The UK’s prerogative passport cancellation powers, while broad in scope, may be less effective as a tool to prevent citizens who pose security risks from returning to the UK from abroad. This is because the Immigration Act 1971 (UK) grants UK citizens a ‘right of abode’, allowing them to enter the UK ‘without let or hindrance’.73 Thus, a citizen who travels to the UK using a foreign passport or fraudulent travel document has a prima facie legal right to enter.74 68 See generally Kent Roach, The 9/11 Effect: Comparative Counter-Terrorism (Cambridge University Press, 2011) ch 5; Helen Fenwick and Gavin Phillipson, ‘UK Counter-Terror Law Post9/11: Initial Acceptance of Extraordinary Measures and the Partial Return to Human Rights Norms’ in Victor V Ramraj et al (eds), Global Anti-Terrorism Law and Policy (Cambridge University Press, 2nd ed, 2012) 481. 69 McGuinness and Gower (n 34) 12 [4]; Theresa May, ‘The Issuing, Withdrawal or Refusal of Passports’ (Written Statement to Parliament, 25 April 2013). 70 For instance, the power is ‘reported to have been used only 16 times between 1947 and 1976’: McGuinness and Gower (n 34) 14 [4.3]. 71 May, ‘The Issuing, Withdrawal or Refusal of Passports’ (n 69). 72 Theresa May, ‘Home Secretary Theresa May on Counter-Terrorism’ (Speech, Royal United Services Institute, 24 November 2014) <www.gov.uk/government/speeches/home-secretarytheresa-may-on-counter-terrorism>, archived at <https://perma.cc/Y9XE-SSBB>. 73 Immigration Act 1971 (UK) s 1(1); see also at s 2(1)(a). 74 Notably, s 1(1) of the Immigration Act also confers a right to leave the UK without let or hindrance. Where a citizen’s UK passport is their sole travel document, however, cancelling their passport effectively renders this right redundant. Advance Copy