The Supreme Court has unanimously held that the Ministry of Defence (MoD) had a duty, under Article 5(4) of the European Court of Human Rights to provide adequate procedural safeguards to detainees at all times, as also required by international humanitarian law, during the conflict in Afghanistan in order to prevent the detention of prisoners becoming arbitrary.

The judgment was delivered in the case of Serdar Mohammed, an Afghan man who was detained by British troops in 2010 and held by them without charge and without access to a lawyer for 110 days, before being handed over to the Afghan Security Services, whom he alleges brutally tortured him.

He was released from detention in Afghanistan to return to his family in 2014.

The Supreme Court held that the minimum safeguards applicable during a non-international armed conflict, such as that in Afghanistan, are those set out in Articles 43 and 78 of the Fourth Geneva Convention of 1949, which require two key elements: (i) impartiality of the detention reviewing authority and (ii) fairness of the procedure.

A majority of six of the Supreme Court Justices found that these basic procedural safeguards were lacking in the case of Mr Mohammed.

It was found that the system of internal review of detention lacked sufficient guarantees of independence and impartiality, and that Mr Mohammed was afforded no opportunity to participate in the reviews.

Accordingly, a majority of the Supreme Court found that Mr Mohammed’s detention was incompatible with Article 5(4) ECHR, since he did not have any effective means of challenging the lawfulness of his detention.

At paragraph 108 of his judgment, Lord Sumption described the “absence of minimal procedural safeguards” in respect of Mr Mohammed’s detention as “unwise as well as legally indefensible”.

A minority of the Justices considered that the adequacy of procedural safeguards should be determined at a full trial in Mr Mohammed’s case.

The ruling also considered the joined appeal of Al-Waheed v MoD. Mr Al Waheed is an Iraqi man who was detained without charge by British Forces in Iraq from 11 February to 28 March 2007. Mr Al Waheed claims he was seriously mistreated by British soldiers and asserts that even on the MoD’s own evidence he should have been released from detention much sooner than he was.

The Supreme Court ruled that British forces in Iraq and Afghanistan were entitled to detain individuals, without breaching the European Convention on Human Rights (‘ECHR’), so long as their detention was necessary for imperative reasons of security.

In the case of Serdar Mohammed, the Court of Appeal held in July 2015 that while the relevant UN Security Council Resolutions (‘UNSCRs’) authorised British forces operating in Afghanistan to capture and detain individuals for up to 96 hours, they were not authorised to hold anyone beyond that period.

In a majority decision, 7 out of 9 Supreme Court Justices overturned the Court of Appeal judgment and concluded that British forces in Iraq and Afghanistan had a legal power to detain individuals for imperative reasons of security, beyond 96 hours if necessary, pursuant to a mandate to use “all necessary measures” under the relevant UN Security Council Resolutions.

They concluded that this legal power modified the UK’s obligations under Article 5(1) ECHR, with the result that the detention of individuals would not be in breach of Article 5(1) ECHR provided that they were detained at all times for imperative reasons of security.

In both the test cases, this issue will be determined following full trials in their claims.

A spokesperson from the law firm Leigh Day, which represents Mr Mohammed and Mr Al-Waheed said: “This judgment provides clarity for the cases currently being brought against the MoD by our clients. It sets the framework, against which the legality of detention in any case will need to be measured.

“Given that the effect of the judgment is to significantly widen the circumstances in which the UK Government can lawfully detain people when overseas, the importance of the unanimous ruling on the minimum procedural safeguards to be provided to detainees, to prevent their detention becoming arbitrary, cannot be over-stated.

“As Lord Mance observed in one of his other judgments delivered today, ‘[a]mong the most long-standing and fundamental [rights] are those represented in Magna Carta’ (paragraph 98 of his judgment in Belhaj & Anor v Straw & Ors).

“The Magna Carta established that imprisonment should not occur without due legal process. By delivering this ruling the Supreme Court has hopefully guarded against the UK setting up its own Guantanamo Bay.”

In a separate judgment delivered today, the Supreme Court allowed the MoD’s appeal against another part of the Court of Appeal’s judgment of July 2015 in respect of the cases of Serdar Mohammed and Iraqi Civilians against the MoD.

This appeal concerned the doctrine of ‘Crown Act of State’, which precludes English courts from passing judgment on cases governed by foreign law, involving sovereign acts of the UK committed abroad, which have been authorised or ratified by the Crown.

The MoD argued that this doctrine precludes the English courts from considering claims pursued under Afghan or Iraqi law by the Claimants for their alleged unlawful detention by British forces and, in the case of the Iraqi Claimants, their transfer from British forces to United States custody.

The Justices agreed that the doctrine may be relied upon by the MoD in respect of the claims and invited further submissions from the parties as to the declarations which should be issued in the claims, within 28 days of the judgment.