A Death Knell for Common Law Domestic Footholds for Unincorporated Treaties? – UK Constitutional Law Association

In September 2024, the Business and Trade Secretary (‘the Secretary of State’)suspended licences authorising the export of items that might be used in carrying out or facilitating Israeli military operations in the Gaza conflict. However, the Secretary of State carved out from that suspension licences for the export of components for F-35 aircraft which could not be identified as destined for Israel (‘the F-35 Carve Out’). The carve out was justified on the basis that suspending licensing for the export of F-35 components would have an impact on the entire F-35 programme, which would “have a profound and immediate impact on international peace and security, would undermine US confidence in the UK and NATO at a critical juncture, would seriously undermine the credibility of the UK as a trusted partner on the international stage, and would undermine a key capability allowing the UK and its closest allies and partners to address current security challenges.”

On 30 June 2025, in Al Haq v Business and Trade Secretary, the Divisional Court (Males LJ and Steyn J) refused permission for judicial review, following a rolled-up hearing, of the F-35 Carve Out. One of the claimant’s grounds was that the F-35 Carve Out placed the United Kingdom in breach of unincorporated treaty obligations (found in Common Article 1 of the Geneva Conventions, Articles 6 and 7 of the Arms Trade Treaty, and Article 1 of the Genocide Convention). In making this argument, the claimant relied on the Secretary of State’s Strategic Export Licensing Criteria (‘the SELC’) – statutory guidance issued under s 9 of the Export Control Act 2002 – which included a criterion requiring “respect for the UK’s international obligations and relevant commitments”, as providing a “domestic foothold” on which the courts could decide whether the F-35 Carve Out did comply with said treaty obligations. The Court rejected this, holding that the SELC did not provide a sufficient domestic foothold.

In this post, I review the Court’s reasoning for so holding, suggesting that it is correct in principle in expressing scepticism of recent case law which has seemingly expressed wholehearted acceptance of the concept of “common law domestic footholds” for unincorporated treaties. However, some novel aspects of the Court’s reasoning provide strong reasons for discarding entirely the concept of common law domestic footholds.

The Court’s Reasoning 

Review of the Case Law

The Court identified the starting point for any discussion on unincorporated treaties as the House of Lords’ seminal decision in JH Rayner (Mincing Lane) Ltd v Department of Trade and Industry (‘International Tin Council’) ([72]). One of the issues arising was whether state members of the ITC (including the UK) were responsible for the ITC’s debts. That depended on the interpretation of the Sixth International Tin Agreement, an unincorporated treaty. Lord Oliver’s speech in that case highlighted, amongst other things, two foundational constitutional principles. First, “a treaty is not part of English law until it has been incorporated into the law by legislation”. Second, the executive’s power under the Royal Prerogative to make treaties does not extend to a power to alter domestic law ([72]).

These principles were relied upon by Lord Reed in R (SG) v Secretary of State for Work and Pensions to hold, in respect of an argument that the imposition of a cap on benefits for non-working households by secondary legislation proceeded on a misinterpretation of the UN Convention on the Rights of the Child, that: “It is firmly established that United Kingdom courts have no jurisdiction to interpret or apply international treaties… it is therefore inappropriate for the courts to purport to decide whether or not the executive has correctly understood an unincorporated treaty obligation” ([75]). As the Court noted in Al Haq, it is apparent that this principle limited the court’s role not only in the interpretation, but also the application of an unincorporated treaty ([76]). The same principle was relied on by Lord Reed in the recent and significant decision of the Supreme Court in R (SC) v Secretary of State for Work and Pensions  to hold that it was “unconstitutional” for a domestic court, in assessing the proportionality of domestic legislation with rights protected under the ECHR, to find that the UK Government has breached an unincorporated treaty, ([77]).

However, against this constitutional orthodoxy and rule – that domestic courts do not have jurisdiction to interpret or apply an unincorporated treaty – stood an exception. This is the notion that the courts will in some circumstances have such jurisdiction, where there is a “domestic foothold” ([83], Al Haq). Although not articulated as such, the concept of the domestic foothold, at least in the context of public law litigation involving unincorporated treaties, refers to the requirement to interpret and apply unincorporated treaties, by  applying conventional public law principles at common law.

The earliest use of this terminology amongst the cases cited to the Court was in R (Campaign for Nuclear Disarmament) v Prime Minister, where the claimant, in a case concerning proposed military action against Iraq, sought to argue that the Prime Minister’s statement to Parliament that “We will always act in accordance with international law” provided such a foothold. The Divisional Court rejected this argument, holding that the domestic courts “are not charged with policing the United Kingdom’s conduct on the international plane”.

The concept of the domestic foothold was recently invoked by judicial review claimants with more success , in an important line of cases concerned with the European Convention on Action against Trafficking in Human Beings (‘ECAT’), culminating in  R (EOG) v Secretary of State for the Home Department ([92]). In these cases, the relevant foothold was guidance issued by the Secretary of State, initially non-statutory but subsequently statutory under s.49 of the Modern Slavery Act 2015, in which she purported to give effect to ECAT. The claimants in these cases argued that where the executive through policy evinces an intention to comply with an unincorporated treaty and fails to do so, that would be a justiciable legal error. Prior to EOG, the Secretary of State operated a longstanding concession that such a failure was justiciable. In EOG, the Home Secretary attempted to resile from this position, relying on the Supreme Court’s judgment in SC. In the end, the Home Secretary eventually conceded that “if in the relevant respects the policy of the Secretary of State was that the Guidance should comply with ECAT it was open to the Court to decide whether it in fact did so and to hold that it was unlawful if it did not”, albeit reserving the right to argue this matter in the Supreme Court. 

The Court of Appeal in EOG therefore did not have to determine the issue, and accordingly what the Court of Appeal said was obiter ([95]). However, Underhill LJ in EOG expressed the view that he found the reasoning of Linden J in the High Court, finding that there was a domestic foothold in these cases, “convincing”. Specifically, Linden J found that, where there is a commitment in executive policy to comply with an unincorporated treaty, the source of any concomitant legal obligation on the executive lays in the executive’s commitment, rather than the treaty itself; thus, it is permissible, in line with “conventional public law principles” to consider what “the requirements of those articles were with a view to deciding whether the policy correctly stated their effect and whether a given decision, taken in accordance with that policy, was lawful”. In other words, this was an application of the “error of law” principle, to determine what the requirements of the relevant provisions of the unincorporated treaty are, and the principle that a public authority must comply with their own published policy unless there is good reason to depart.

The reference to “conventional public law principles” by Linden J appears to reflect an acceptance of the concept of common law domestic footholds, in relation to the whole swathe of obligations that public law imposes on public authorities. This ECAT line of case law and reasoning lay the foundation on which the claimant in Al Haq argued there was a domestic foothold in its case ([110]).

The Court in Al Haq noted the claimant’s reliance on two further significant cases, Launder and Kebeline, in which the House of Lords had determined that a public authority’s acknowledgement that it had sought to comply with provisions of the ECHR, at a time when its status in English law was of an unincorporated treaty, was sufficient to create a “domestic foothold” ([101]). The Court’s reading of these two cases is significant, in two respects. First, it expressed the view that Lord Hope’s invocation of the Article 6 right to fair trial in Launder was “an irrelevance”. This was because the central legal question for the Secretary of State in that case was whether, under domestic extradition law, extradition would be unjust or oppressive ([99]). This would necessarily take account of whether the claimant would receive a fair trial. The invocation of Article 6, arising from the Secretary of State’s commitment to complying with the UK’s treaty obligations under the ECHR, therefore added little.

Second, it considered that an understanding of Kebeline and Launder as standing for the proposition that the House of Lords was recognising a principle that the courts could interpret and apply an unincorporated treaty, solely on the basis that the executive had expressed a commitment to said treaty’s provisions, would “have represented a major inroad into the basic principle that the court has no jurisdiction to interpret or apply the terms of such a treaty” ([102]). This approach was said to have been rejected in R (Corner House Research) v Director of the Serious Fraud Office, where the judgments of Lord Bingham and Lord Brown sought to confine the dicta in Kebeline and Launder to the “particular context in which they arose” ([106]). Those were cases “concerned with individual rights arising under the ECHR, at a time when the Convention had not yet been incorporated into domestic law, but everybody knew that it soon would be”.

Further, the Court also noted that in Corner House, Lord Brown expressed agreement with an influential article ([2008] LQR 388) by Philip Sales QC (now Lord Sales) and Joanne Clement, which opined that, when courts are called on to examine questions of international law which are uncertain and which they do not have the authority to determine themselves, a “tenable view” approach should be adopted ([105]). This approach has been subsequently adopted by the Court of Appeal, including recently in R (Friends of the Earth) v Secretary of State for International Trade ([109]), a case involving challenge to the UK Government’s assessment that its financing of a liquefied natural gas facility in Mozambique was consistent with its obligations pursuant to the Paris Agreement. 

Application to the Facts

Having considered the case law, the Court noted the superficial attractiveness of the argument that the SELC, being statutory guidance, was analogous to the statutory guidance issued under the Modern Slavery Act 2015 in EOG, in which a domestic foothold was found relying on the Secretary of State’s policy to comply with ECAT ([110]). However, three independent reasons meant that the SELC did not provide a common law domestic foothold in this case ([111]).

First, the nature of the decision in this case. Properly analysed, the decision concerned whether the UK would continue to participate in a defence programme with other countries, engaging issues of “defence, international peace, national security and the conduct of foreign relations”. These were all issues which are “reserved under our constitution to the judgment of the executive which is democratically accountable to Parliament and the electorate” ([112]).

Second, the Secretary of State did not purport to apply the guidance in the SELC, having referred in the decision letter to the F-35 Carve Out as an “exceptional measure”, and recognising in his parliamentary statement that the SELC’s application was “without prejudice to the application to specific cases of specific measures as may be announced to Parliament from time to time” ([113]). The F-35 Carve Out was therefore a decision taken outside the SELC’s framework, and there was no basis to apply the public law principle requiring the Secretary of State to comply with his own policy i.e. the SELC ([114]).

Third, even if the Secretary of State had purported to comply with the SELC, and the SELC could be seen as giving rise to a domestic public law obligation, this was a case where the tenability approach was “clearly appropriate”, and the Secretary’s view met this threshold ([116]).

Finally, the Court also rejected the claimant’s alternative case, relying on the Secretary of State’s decision letter pertaining to the F-35 Carve Out, in which he expressed a view that his decision was consistent with the “UK’s… international legal obligations” as providing a domestic foothold. The Court held that finding otherwise would be inconsistent with both Campaign for Nuclear Disarmament and Corner House ([117]).

A Welcome Scepticism

The Court’s approach to the concept of common law domestic footholds is quite clearly one of scepticism. This is seen in at least three aspects. First, its limiting of the concept by creating a “carve out” for areas of “high policy” ([90]). Second, its reading of Kebeline and Launder as being limited to the very narrow context of interpreting the ECHR qua unincorporated treaty at a time when it was known by everyone that it would very soon be incorporated ([106]). Third, its suggestion that any alternative reading of Kebeline and Launder would represent a “major inroad into the basic principle that the court has no jurisdiction to interpret or apply” unincorporated treaties ([102]).

In this author’s view, such scepticism is welcome. The notion of common law domestic footholds for unincorporated treaties flatly breaches the two important constitutional principles identified in International Tin Council. This can be seen using the example of the ECAT cases e.g. EOG. First, by holding the Secretary of State to her policy intent to comply with ECAT, thereby creating legal obligations, the Court of Appeal made an unincorporated treaty “part of English law”. Second, by finding that the Secretary of State self-imposed binding legal obligations to comply with ECAT, the Court of Appeal created a situation whereby the executive “altered domestic law”. The crux of the contrary argument, that the court is simply performing a form of rationality review – whereby the courts are not directly using unincorporated treaties to create legal obligations but recognising the executive’s commitments as a fact relevant to assessing the rationality of their decisions – is unpersuasive.

Even if such an argument is made out, it is inconsistent with the constitutional principle that an unincorporated treaty is not part of domestic law. A useful analogy is the law of legitimate expectations. One of its principles is that legitimate expectations cannot be invoked if the expectation was represented in breach of statutory duty: Corporation of the Hall of Arts and Sciences v The Albert Court Residents’ Association at [35]. The underlying rationale is that common law principles cannot be invoked in a way to undercut basic constitutional principle, in this case parliamentary sovereignty. This should have been applied in EOG to refuse consideration of a policy commitment to comply with an unincorporated treaty when assessing rationality, to avoid creating domestic legal obligations.

Whilst it might be highlighted that other common law jurisdictions, where the principle of parliamentary sovereignty also applies, have utilised public law doctrine at common law to interpret and apply unincorporated treaties, as Sales and Clement explain in their influential article,

the constitutional understanding in the United Kingdom… has been that development of the law in this area is primarily for Parliament rather than the courts… therefore considerable and increasing caution has to be exercised when reference is made to the case law of such other jurisdictions, and it cannot be simply and straightforwardly applied in the English context.

Inconsistencies/Difficulties in the Reasoning for Common Law Domestic Footholds

We can in fact go further: the Court’s decision in Al Haq, in an attempt to rationalise the case law on common law domestic footholds, with its welcome scepticism of the concept in this case, provides two strong reasons why the concept should be entirely discarded.

1. Enlarging the Scope of Non-justiciability

First, due to its apparent discomfort with the implications of the concept of common law domestic footholds in the context of cases engaging matters of high policy, the Court has arbitrarily enlarged the scope of the doctrine of non-justiciability, in a manner that is inconsistent with longstanding authority.

As stated above, the Court’s first independent reason for rejecting the analogous application of EOG in Al Haq was due to the nature of the decision in the case, which engaged issues of “defence, international peace, national security and the conduct of foreign relations”. This seems to be an argument rooted in non-justiciability on grounds of engagement of high policy, as seen from the Court’s discussion at [90] where its consideration of “deference” lapsed into suggesting that in some cases, there is not only “very limited… scope” but sometimes “no further scope for review” once it is identified that a ministerial decision engages high policy.

However, in a judgment handed down one day after Al Haq, Campbell v Attorney General, a separately constituted Divisional Court articulated the classical statement of the modern judicial review court’s approach to high policy as follows:

The courts have continued to regard certain subject matters as inappropriate for judicial determination for institutional and constitutional reasons, but they have tended to give effect to these conclusions by limiting or modifying the grounds on which the decision can be challenged or by according a broad margin of discretion or ascribing particular weight to the view of the decision maker, rather than by categorising the decision as non-justiciable simpliciter. (emphasis added)

More specifically, on the specific topic of national security which was identified by the Court in Al Haq as justifying a “carve-out” for matters of high policy in relation to the concept of common law domestic footholds, the Court in Campbell said that “The invocation of national security no longer operates as a complete bar to reviewability, though it is now well established that “great weight” and “appropriate respect” should be accorded to the national security assessments of the executive”.

Put simply, the engagement of areas of high policy as identified by the Court in Al Haq might justify a greater degree of deference (or margin of appreciation) to the decision-maker, but it does not justify complete non-justiciability in the manner envisaged by the Court’s reasoning in Al Haq.

2. Arbitrary Distinction Between Ministerial Statements and Policy Documents

Second, the Court in Al Haq has effectively created an arbitrary distinction between general ministerial decisions (whether reflected in a formal decision or statement), on the one hand, and policy documents on the other, in the sphere of common law domestic footholds which does not otherwise exist generally in the common law. This is seen in the Court’s reasoning at [117], where it states that the Secretary’s self-direction in the decision letter in this case could not create a domestic foothold, as it “could not stand” with Campaign for Nuclear Disarmament and Corner House, both of which concerned several public statements made by a Minister (whether to Parliament or otherwise). Although the point is not stated, this seems to reflect a view that “ministerial decisions” – broadly construed – will not be sufficient to engender common law domestic footholds, whereas policy guidance (such as in EOG, and the SELC were it not for the three independent reasons identified by the Court in this case) would do so.

That the distinction being drawn is between ministerial decisions (broadly construed), and policy documents (as in EOG), is seen from the citation by the Court in Al Haq (at [64]) of Lord Brown’s reasoning in Corner House at [67] in finding there was no domestic foothold in that case, which was

It simply cannot be the law that, provided only a public officer asserts that his decision accords with the state’s international obligations, the courts will entertain a challenge to the decision based upon his arguable misunderstanding of that obligation and then itself decide the point of international law at issue.

The concern of the Court in Al Haq thus did not seem to be that the decision letter in question was not “public-facing”, whereas policy documents are, especially given the recognition that the substance of the decision letter was “announced in Parliament on the same day in a written statement” (Al Haq at [5]).

This is an unprincipled distinction which does not otherwise exist in public law. The starting point is that all material errors of law in public authority decision-making are justiciable: Council of Civil Service Unions v Minister for the Civil Service. There is no distinction between errors made in less “formal” documents/statements, or those documents/statements which are more “transient”, if this is the distinction sought to be struck by the Court in Al Haq. Certainly, challenges premised on errors of law against e.g. ministerial statements or letters sent by public authorities do not generally fail for non-justiciability. It is not clear why, or how, a distinction between ministerial decisions and policy/guidance documents (again, if that is the distinction being made) should be drawn when it comes to the ability to create common law domestic footholds. As a matter of principle, both are capable of evincing genuine policy intentions. Indeed, in some cases, ministerial decisions (whether in letters or statements) are articulated or written personally by a responsible minister, which may be thought to reflect a greater level of seriousness as to articulated intent than, for example, a policy document which may simply be issued in the name of a minister’s office.

Conclusion

Overall, the Divisional Court’s judgment in Al Haq provides a welcome scepticism of the concept of common law domestic footholds for unincorporated treaties. The concept curtails two important constitutional principles. First, the principle that a treaty is not part of English law until it has been incorporated into law by legislation. Second, the executive’s power to make treaties under the Royal Prerogative does not extend to a power to alter domestic law.

However, in seeking to limit the application of the concept against the backdrop of recent authorities which have brought into sharp focus its application in domestic law, the Court’s judgment has introduced further incongruence into the concept, confirming that attempts to recognise it, even with a limited scope, are ripe to invite further inconsistency with other core public law principles. This presents strong reasons for considering that the concept should be discarded in its entirety.

I am grateful to the editors of the blog and Dane Luo for their helpful comments on earlier drafts.

Gabriel Tan, Incoming MPhil Law student, University of Oxford.

(Suggested citation: G. Tan, ‘R (Al-Haq) v Business and Trade Secretary: A Death Knell for Common Law Domestic Footholds for Unincorporated Treaties?’, U.K. Const. L. Blog (7th July 2025) (available at https://ukconstitutionallaw.org/))