Treaty accountability

By: Arabella Lang

A distinguished panel at Public Law Project’s recent conference on accountability and the constitution considered the issue of treaty accountability in the UK – a topic that without a developed field of foreign relations law in the UK can often fall between the cracks. In this post I will pick up on a few of the questions raised at the conference. Is exceptional treatment of treaties justified under the constitution? Why has Parliament shown so little interest in holding the government to account for its treaty actions? When and why might accountability come from the courts instead?

Sovereignty and accountability

The notion of dualism, which is based on the proposition that international law and domestic law operate in independent spheres, is often cited as a justification for the demonstrable lack of parliamentary engagement with treaties unless and until implementing legislation is required. The argument is that dualism protects parliamentary sovereignty from the executive’s prerogative power to make treaties: unincorporated treaties do not impinge on Parliament’s legislative sovereignty, and any treaty-related changes to domestic law follow standard legislative procedures.

But there is another fundamental constitutional principle at play here: parliamentary accountability. Ministers are accountable to Parliament for their exercise of the treaty-making power. What does this principle entail?

Professor Campbell McLachlan made a strong case for accountability not only as a political convention but also a legal duty. Under this proposition, the government would be acting unlawfully if it curtailed political accountability. This of course was the point on which the Miller/Cherry prorogation case turned, but Professor McLachlan presented it as a principle of “great antiquity” that in the past was enforced in relation to treaties by impeachment.

David Lawrence argued that treaty accountability matters because some modern treaties “blur the distinction between domestic and international law”. He gave the example of regulatory reform required by trade treaties that either ties Parliament’s hands by predetermining legislative change, or sets policy on controversial matters without requiring implementing legislation. For instance, digital trade provisions illustrate how the UK’s post-Brexit bilateral trade agreements may erode individual rights and constrain Parliament’s ability to protect data and privacy rights in future. In these examples, dualism is not enough to protect either parliamentary sovereignty or citizens, and there is little opportunity to debate the balance between competing interests. Without a growth in scrutiny, the expansion of the scope and effects of treaties in recent years therefore amounts to a shift in power to the executive.

Parliamentary accountability in practice

Despite its importance, parliamentary accountability for the government’s treaty actions is still underdeveloped.

Before Brexit there was little other than some short ‘information paragraphs’ from the Lords Secondary Legislation Scrutiny Committee, and occasional inquiries by the Joint Committee on Human Rights. The treaty provisions of the Constitutional Reform and Governance Act 2010 (CRAG) do not require parliamentary debates or votes, nor do they require or facilitate any scrutiny. Jill Barrett noted that CRAG did not go as far as it might have done, for there was little public pressure or parliamentary appetite. This was partly because at that time many important treaty matters were handled on the UK’s behalf by the EU and were subject to its stronger scrutiny mechanisms.

Parliament has recently strengthened its treaty scrutiny: the House of Lords has created a new International Agreements Committee (IAC) and the Commons International Trade Committee (ITC) has started scrutinising trade negotiations. And the government has made some commitments to providing information, debates and extra time for scrutinising some finalised trade treaties. But it has done little to secure meaningful accountability before and during negotiations when a treaty could still be amended: ‘any scrutiny that occurs is essentially in the gift of the Government of the day’. It has also consistently opposed a new requirement for Parliament to approve treaties – a power which the IAC now considers essential to effective scrutiny of trade and other important treaties.

In the Commons, there is little appetite for treaty scrutiny beyond the ITC. There are many reasons for this: some treaties are large, complex and cross-cutting (always a challenge for a committee system that mirrors government departments) while others are routine and technical; the statutory scrutiny period under CRAG comes too late to amend the content of the treaty; and without a treaty approval requirement there is little incentive to engage.

Enforcing a duty of accountability

Without government support, there is little that Parliament can do to increase this scrutiny, for instance by changing its own committees or rules of procedure. Might the courts consider whether this level of scrutiny meets the constitutional requirements of accountability?

As Naina Patel powerfully demonstrated, the courts have made significant inroads into the principle of non-recognition of unincorporated treaties. For example, they will try to interpret domestic legislation and common law so as to be compatible with treaty requirements, and they may use freestanding public law principles such as legitimate expectations or misdirection in law.

In doing so, they have sometimes assumed a level of treaty scrutiny that is hard to evidence. For example, in 2015 Lord Kerr, in his dissenting judgment in the Supreme Court case of SG, argued that ‘Standards expressed in international treaties or conventions dealing with human rights to which the UK has subscribed must be presumed to be the product of extensive and enlightened consideration.’ He used this argument to support his proposition that unincorporated human rights treaties should be directly enforceable in the English courts (a position not accepted by the majority in that case, and firmly rejected in the 2021 Supreme Court case of SC). This proposition is perhaps constitutionally easier to accept if treaties are considered to have Parliament’s imprimatur.

But while the courts will sometimes consider treaty provisions to be relevant to their considerations, the government’s exercise of treaty powers is rarely ruled justiciable: ‘the general rule is that the power to make or unmake treaties is exercisable without legislative authority and that the exercise of that power is not reviewable by the courts’. Reasons for this include that it is a prerogative power, that it concerns foreign relations, and that the government is politically accountable to Parliament for its treaty powers. But none of these on their own necessarily precludes judicial review.

A trigger for justiciability is whether the exercise of the treaty power directly engages individual rights. If this is met, then the door may be opened to a court adjudicating on whether in the exercise of its treaty power the government has sufficiently met its obligation of accountability to Parliament.

This would of course raise many of the same objections of judicial intervention in political matters as we have seen with Miller/Cherry. As Alexander Horne noted, Article 9 of the Bill of Rights (‘the Freedom of Speech and Debates or Proceedings in Parliament ought not to be impeached or questioned in any Court or Place out of Parliament’) could be engaged. However, to determine the scope of Article 9 in any particular context it is necessary to focus on its purpose, which is not protecting executive acts from scrutiny.


This discussion leads to the intriguing conclusion that unless the government allows effective scrutiny by Parliament of treaties that affect rights in the UK, it may be in breach of its duty of accountability, opening the door for the courts may intervene. If this is so, then it may be in the interests of a government that seeks to constrain judicial intervention to facilitate adequate parliamentary scrutiny of treaties.

With many thanks to Campbell McLachlan, Jill Barrett, Alexander Horne, David Lawrence and Naina Patel. Any errors remain my own.

Arabella Lang is Deputy Research Director of the Public Law Project. She previously worked with the House of Commons research service and committees, where she established and ran the Parliament and Treaties Hub.

The Constitution Society is committed to the promotion of informed debate and is politically impartial. Any views expressed in this article are the personal views of the author and not those of The Constitution Society.