encouraged others to do so. In many cases, there is no evidence of them being involved in preparatory
crimes or conspiracies and thus they technically can return to Britain without any legal consequences.
This has led to a frenzied debated in the media about whether we need to enact a new treason offence.
The Home Secretary has grasped penal populism with alacrity, but what we need are nuanced and
reasoned arguments so we can decide what legal responses, if any, are appropriate. I shall start by trying
to demonstrate that the law of treason offers nothing in such cases. More generally, I shall argue that the
law of treason is not apt for tackling the modern problem of terrorism and therefore should not be
expanded. Thereafter, I shall refute the argument that we need a new offence of treason because our
current terrorism laws are not sufficiently extensive and the claim that our current law does not allow for
severe enough punishments. It will be argued if anything terrorism is over-criminalised and dispropor-
tionately punished. Finally, I shall argue that the common law offence of outraging public decency could
apply to some returning ISIS brides but that we should be thinking hard about the need for a criminal law
response when we are relying on these sorts of vague offences. The bare act of deserting Britain to marry
a militant has the potential to outrage public decency, but it is more likely the offence would be applied
when the returning bride makes hateful comments in the media.
I examine whether there are lacunae in th e law for cases wher e people have trav elled abroad and
married and/or associated with terrorists and war criminals. It will be argued that it is not a problem
of substantive law, but one of insufficient evidence to prosecute. Having said that, if we were to
criminalise the act of association
under a broad perfidy offence, it would catch cases where we are
unable to prove that the associate (wife, sister, friend and so on) assisted or encouraged terrorism or
war crimes. A recent report by Policy Exchange, authored by a shadow minister; a Tory MP—who is
a former soldier, a barrister/broadcaster and a leading academic,
argues that the law of terrorism is
inadequate in many cases and does not provide sufficient sentences for certain acts involving
betrayal. The makeup of the authorship of that report means it is likely to be influential.
Ishalltrytoaddresssomeoftheconcernsraisedby the authors of that report and put forward robust
A new offence of treason would only plug the evidential gap by making the bare act of betrayal
itself criminal (the bare act of a British citizen associating in anyway with enemies of Britain) but that
act of betrayal in itself would hardly justify the sorts of sentences that the Policy Exchange report calls
for. The current problem is one of a lack of evidence. It might be assumed that some of the ISIS brides
took a more than passive role, but we cannot try people on a statistic guess. We need evidenceon what
the particular ISIS bride was intending and evidence about what actions she personally undertook.
We need evidence to support any allegations of active involvement in armed conflicts involving
Britain forces. There may well be evidence, but until it is discovered these ladies remain innocent
until proven guilty.
2. I do not intend to examine the sorts of crimes that might have been perpetrated by the associates of Shamima Begum. For an
examination of the core offences that might have been assisted or encouraged, see Antonio Cassese, Cassese’s International
3. R Ekins, P Hennessey, T Tugendhat and K Mahmood, Aiding the Enemy: How and Why to Restore the Law of Treason (Policy
Exchange, London 2018).
4. The Policy Exchange webpage claims: ‘The report’s recommendation for reform of the law of treason was taken up in the
House of Lords last year, leading to amendments being proposed to the Counter-Terrorism and Border Security Bill. Last
month, the report was raised again in both Houses of Parliament, with the Rt Hon Sajid Javid MP, the Home Secretary,
confirming that the Government is examining the idea closely’. See Policy Exchage’s comments under its advert for: ‘Cry
Treason!Does the UK need to restore the law of treason?’.
5. Research looking at them as a group does not give us evidence for prosecuting individuals. For some insights into the role of
women in ISIS, see L Sjoberg, ‘Jihadi Brides and Female Volunteers: Reading the Islamic State’s War to see Gender and
Agency in Conflict Dynamics’ (2017) 35(3) Conflict Management and Peace Science 296; D Chatterjee, ‘Gendering ISIS and
Mapping the Role of Women’ (2016) 3(2) Contemporary Review of the Middle East 201.
20 The Journal of Criminal Law 84(1)