The United Kingdom Court of Appeal handed down its judgment in Serdar Mohammed v. Ministry of Defense last Thursday. The decision, which assessed the lawfulness of the 110-day security detention of a suspected Taliban commander by UK forces in Afghanistan in 2010, sheds important light on how human rights law and international humanitarian law interact in the context of security detention in an extraterritorial non-international armed conflict.

The Court ruled that the United Kingdom had sufficient legal authority and grounds to hold Mohammed for the first 96 hours of his detention and, for those four days, the Court also ruled that the United Kingdom afforded him appropriate procedural guarantees. The same wasn’t true for the next 106 days of his captivity. The Court made this ruling on the basis of Article 5 (right to liberty and security) of the European Convention on Human Rights.

As to the substance of the decision, the Court had to determine the relationship between human rights law and international humanitarian law. Without reciting all the points covered, one of the more important parts of the decision was the Court’s reaction to the Secretary of State’s claim that Article 5 can be modified under the notion that international humanitarian law is lex specialis and therefore its rules should take primacy over human rights law. The Secretary of State based its claim on Hassan v. United Kingdom (ECtHR) but, as the Justices rightly noted, that case involved an international armed conflict (IAC) and addressed a legal matter (detention) that is covered by detailed rules of international humanitarian law. To determine if Hassan was, in fact, relevant, the Justices said they needed to determine if the international humanitarian law of non-international armed conflict (NIAC) similarly contained relevant detention rules.

This brings us to the heart of the case and as we’ll see in a moment, the Secretary of State’s reliance on Hassan falls flat . . .  sort of. 

Before determining the relationship between Article 5 and IHL in the context of a NAIC, the Court sought to determine what, if any, other legal authority may have allowed the United Kingdom to detain Mohammed in Afghanistan. The Court looked to the UN Security Council and Afghan domestic law. (The Court noted that it did not assess UK domestic law in this portion of the decision because the Secretary of State did not raise it.)

With respect to Afghan law, there was no legal authority that allowed detention beyond 72 hours. With respect to the UN Security Council, the Justices determined that the Council, through Resolution 1890, provided ISAF with an authority to detain and, in turn, ISAF decided to limit that detention authority to 96 hours, and only 96 hours. The United Kingdom, therefore, derived an authority to detain from the Council. (The Court similarly concluded that ISAF’s detention rules, and the United Kingdom’s own detention rules, set out sufficient grounds for detention.)

With the first 96 hours covered legally, the Justices then assessed whether international humanitarian law granted an authority and grounds for the United Kingdom to detain beyond 96 hours. Ultimately, their conclusion affirmed those of us (me included) who believe that international humanitarian law, which does not contain an explicit authority to detain in NIAC, does not contain an implied authority to detain in NIAC. The Justices were also not convinced that customary international law provided an authority for security detention in NIAC.

The Justices came to this conclusion after reviewing a wide range of legal arguments, literature, state practice, and opinio juris. The Court rejected the notion that an authority to detain under IHL exists in the absence of its express prohibition under IHL. It also rejected the argument that the IHL of NIAC contains an implicit authority to detain and, in particular, that an authority under IHL to use lethal force implies the less grave authority to detain. In support of its view, the Court noted that States purposefully refused to grant the authority to detain under IHL so to guard from giving that same authority to non-state armed groups; recognized that States clearly demonstrated their desire to retain certain sovereign authorities under international law, which include an ability to detain and maintain law and order on their own terms; and found it problematic that if an authority to detain could be implied in the IHL and NIAC, that body of rules contains no grounds or procedures for security detention.

Moreover, in so much as proponents for an implied detention authority rely on the Geneva Convention rules for POWs and internees (which apply to international armed conflict) to fill this gap, the Court labeled this approach “highly controversial” and said that there is a “certain artificiality” in basing the authority to detain in the IHL that applies to a non-international armed conflict while basing its scope and the safeguards on the IHL that applies in international armed conflict.

The Court then had to assess what procedural safeguards the United Kingdom needed to afford Mohammed and whether it did so sufficiently. The Court does this through an assessment of what is called “irreducible core procedural requirements”—requirements put forth by the Secretary of State (which are based heavily on IHL) but which the Court sees as being common to IHRL. These requirements were 1) humane treatment, 2) the entitlement of detainees to be informed promptly of the reasons for their detention in a language they understand, and 3) periodical review by an impartial and objective authority to ensure that if, prior to the cessation of hostilities, there ceased to be imperative reasons of security to detain a person, he or she should be released.

Oddly, having discounted Hassan, the Court nonetheless measured the United Kingdom’s actions largely against IHRL and IHL standards, perhaps as a way to play the Secretary of State at its own game of using IHL. But, in doing so, the Court quickly skimmed over the important legal question of whether a State must make a formal Article 15 derogation to implement a security detention regime that limits Article 5 rights and allows something other than a court to determine the lawfulness of a person’s detention. Instead, the Court jumped past this issue and determined that the periodic review was not impartial and objective; expressed “real doubt that it is authorised to determine ‘the lawfulness’ of continued detention;” and said there was no opportunity of the detainee to participate in the reviews of his detention.

The Justices conclude “even if Article 5 had to be modified to reflect the fact that this detention was in the course of a non-international armed conflict, the minimum procedural safeguards required by international law in such a conflict would not have been met.”

In addition to its substance, the context in which this decision arrived is important. Justice Lloyd Jones and Justice Beaston add fodder to the ongoing debate about the inappropriateness of extending the Convention’s jurisdiction to overseas military operations. For those unfamiliar, the gist of the European Court of Human Rights’ interpretation is that the Convention applies extraterritorially when a State has effective control over an area or when it has power and control over an individual, regardless of where that territory or individual is located.

The Justices say that various practical and legal difficulties arise from applying the Strasburg court’s interpretations on extraterritoriality and they even express “significant legal reservations” about the Strasburg court’s interpretations (interpretations which the UK Supreme Court has taken on board). While practical and legal difficulties exist, this is not a new challenge for law and it’s no reason to throw the baby (i.e., the European Convention) out with the bath water. For that reason it was appropriate, indeed required, that the Justices, be it somewhat begrudgingly, applied the Strasburg court’s views.

Before they did so, however, they pointed the Secretary of State to a legislative fix. Legislation, the Justices say, “might have taken the form of a bar of specified claims by foreign nationals or have provided for specific authority for HM [Her Majesty’s] armed forces to detain in operations overseas.” If the Secretary of State seriously considers proposing either of these legislative approaches, the second suggestion seems to sit best with the Convention and, in particular, its article on the right to an effective remedy.