Introduction
The United Kingdom’s Labour government has defined its approach to international law as it applies in the context of UK foreign policy. It is called ‘progressive realism’. In a lecture given to the Royal United Services Institute (RUSI) on 29 May 2025 , the Attorney General Lord Hermer KC set out the government’s approach to international law. Building on the Foreign Secretary David Lammy’s early Locarno speech on the future of UK foreign policy (9 January 2025) , the Attorney General put legal meat on the bones of the Foreign Secretary’s approach.
The Attorney General’s lecture is of particular interest to lawyers and others not just as it sets out the government’s approach to international law at a time when the latter is under considerable strain around the world but also because it seeks to re-state the hard-edged benefits that accrue to the UK in making use of instruments of international law and in conserving that law’s general application.

In essence the Foreign Secretary and the Attorney General seek to articulate a contemporary social democratic approach to foreign policy, international relations, and international law.

Progressive realism in outline
In his lecture the Attorney General set out the legal underpinning for Progressive Realism, stating that it “combines both a pragmatic approach to the UK’s national interests with a principled commitment to a rules-based international order.” For him, the context the government faces as regards global security includes the Russian invasion of Ukraine, the conflict in Gaza, the restriction of freedom of navigation and trade through the Red Sea, the conflict in Sudan, actions by hostile states within the UK (espionage, the targeting of critical infrastructure, and the threatening of UK-based dissidents) and ‘criminal gangs…fuelling irregular migration’. The last of these is probably best described as a contested domestic political issue rather than a threat a global security but, that quibble aside, what the rest of the list shows is a concern with international law that extends beyond free-trade treaties and the like to the use and abuse of international law where there is a use of force or threat of the same by state or non-state actors.

To justify and make good the utility of progressive realism as guiding principle for UK foreign policy and the UK approach to international law, the Attorney General sets out to tackle two schools of criticism: the first he calls romantic idealism, the second pseudo realism. To make sense of why his analysis is important it is necessary to take a step back and consider the nature of realism itself.

Realism

First and foremost, realism is a theory of international relations that seeks to make sense of the global political scene. While it has a genealogy in earlier writings, in its 20th Century iteration, it is concerned with states as the key international actors and the struggle for power among them. It has a large literature. Further it takes different forms. One strand of classical realism (see for example Hans Morgenthau’s Politics Among Nations (1948)) explains state behaviour by reference to human nature and the domestic political concerns within states. Later, neo-realist writings (see for example Kenneth Walz’s Theory of International Politics (1979)) consider state behaviour to be conditioned by the structure of the international system and the capabilities, vulnerabilities, and potential of each state relative to its place in that structure and thus relative to the like factors appertaining other states in the system.

For present purposes, what matters is that classical realism developed a sustained critique of the particular attempt, after the First World War, to use international law and the mechanisms of the League of Nations to prohibit war and thus to constrain strain states in the exercise of their power; the key text here is E.H. Carr’s The Twenty Years’ Crisis (1939). Realist writers are particularly critical where international law embodies ethical values that fail to regulate the conduct of states and which want for any effective enforcement mechanism.

Realism is a theory of international relations that sets out to explain the behaviours of states. To that extent that it is correct, all states act in a realist manner. When a state sets its foreign policy as self-consciously realist (as the Foreign Secretary and the Attorney General seek to do for the UK), what matters is the particular content of that policy rather than the fact it is branded as realist. That said, albeit that it is a theory of international relations, realism has its used in the shaping of a state’s foreign policy. For example, while the late-20th Century school of neo-realism, with its structural approach to the analysis of the international system, may not seem to readily lend itself to conversion into principles of foreign policy, it does aid a sober analysis of the international environment within which UK foreign policy choices fall to be made, as well as assisting in a frank appraisal of the UK’s capabilities (economic and military), its vulnerabilities, and its potential.

Romantic idealism
In his lecture the Attorney General takes aim first at those he describes as romantic idealists; those for whom “international law, conceived as the reign of moral principle, provides a complete answer to any question.” He states “to these idealistic champions, British foreign policy is simple. Follow moral principle wherever it takes us…”
In substance, the charge is that they are concerned solely with the ethical content of international law, seeking to use the UK as an international actor to cast public aspersions on all who fall short by saying that “[w]e should always call out our partners, with different types of governments, regardless of whether the criticism works or whether quiet diplomacy might more effectively produce results…[p]ositioning ourselves as the pious priest, confining ourselves to the comfort of self-righteous declaration, would confine us to irrelevance in global affairs..”

The criticism is three-fold. First, that such idealists focus solely on the ethical content of international law. Second, that they are blind to the inter-relationship between international law and the exercise of power by states, where each conditions the other. Third, that as a matter of technique, their prescriptions for the setting of UK foreign policy and its exercise are ineffective to achieve the ends they seek.

These criticisms seem designed to head-off the criticisms of lawyers, activists, and others who fail to integrate into their critique of UK foreign policy an analysis of the context of the international political environment within which UK foreign policy and practice is articulated. Where there is such a failure, there is some merit in the criticisms. However, such a characterisation of idealism, taken to its logically conclusion, would blunt almost any criticism for an alleged want of appreciation of the actual balancing of interests and prioritisation that takes when the UK makes particular choices in its conduct of foreign affairs. Further, the priest’s piety or the lawyer’s fidelity to the ethical content of international law may be what is required when calling a recalcitrant sinner to order.

In truth, much of the ethically-based, legally-focused, criticism of UK foreign policy that is made is acutely sensitive to the exhortatory character of its demands and the relative weight and position of the UK itself in the society of states. Moreover, the values articulated by idealists (be they lawyers, activists, or others) enrich the climate of opinion domestically and internationally within which power its exercised and contribute both to an emancipatory agenda and to a discursive politics of which no progressive party has cause to be afraid.

Pseudo realism
Having considered romantic idealism on the one hand, the Attorney General takes aims secondly at those he calls pseudo-realists, those he says who “demand that in these volatile times we must abandon our longstanding commitment to international law and to moral principle.” This could include those who seek to encourage a state to break its international treaty commitments in the exercise of its sovereign right to advance its self-determined interests, as well as those who seek a state’s withdrawal from certain international treaties.

Among pseudo-realist motivations is the concern that certain international treaties embody ethical constraints on the exercise of state power that impermissibly limit its operation, not least where the policy choices behind that exercise of state power spring from a democratic mandate. In practice, the target of his criticism’s is those who seek the UK’s withdrawal from the European Convention on Human Rights (ECHR) and other international legal commitments in pursuit of advancing UK state power free of ethical encumbrance or an obligation towards a counter-party. The Attorney General considers that pseudo-realists “advocate for the UK flexing its muscles to make sure it has a seat at the table in the rooms of the powerful where new rules and norms will be forged in the furnace of raw power…”

In defining pseudo-realists in this way, the Attorney General identifies a blind spot in the arguments of those who seek the UK’s withdrawal from international laws that seek to limit the exercise of state power on ethical grounds. As noted, those who advocate withdrawal from the ECHR see it as an unwarranted ethical constraint that limits the exercise of democratic will. However, they miss the obvious point that the ECHR and other such international instruments are also the exercise of state power (by the UK and other states) and that the projection of UK state power is advanced by the contribution of these legal instruments to shaping the character of the international environment in which the UK operates by inclining that environment as far as possible towards its domestic values.

A society of states, regionally in Europe or even globally, that adheres to liberal values (democratic control, separation of powers, limited government, etc.), creates a more benign environment for the UK to advance its interests abroad and to maintain and secure its internal character.

Internationally, such treaties facilitate a high level of trust between states, enabling UK objectives to be advanced co-operatively rather than in conflict with others and thus at less cost.

Domestically, they assist as there is less pressure on the UK to alter its civic political structure, principles, and values (taken together, civic virtues) in order to accommodate more powerful authoritarian states who seek to exercise power over it, whether politically or economically. It is easier to develop foreign policy or economic policy towards Russia and China while preserving the UK’s civic virtues, by participating in the Council of Europe and other regional arrangements with like-minded states such as France and Germany, than it would be were the UK not to participate in them.

The ECHR and the Council of Europe regional system may be seen as an exercise in advancing internationalising ethical standards so as to constrain state power (a worthy exercise in itself) but they may also be seen as the projection of state power in its international articulation of the civic virtues that define the internal character of the UK and other states in the European region, so that each such state secures a more benign environment in which to operate to its own benefit. Looked at in this way there is no conflict between ethically-based international law and the exercise of power; UK interests are directly, indeed selfishly, advanced by participation.

The content of progressive realism
Having criticised the poles of romantic idealism and pseudo-realism, the Attorney General rejects both and argues for progressive realism as “the principled pragmatism that guides this Government’s foreign and security policy…” He gives four reasons for this approach.

First, “a selective, or ‘pick and mix’ approach to international law” by the UK will lead to its disintegration. There can be no deviation in the national interest. Ministers are obliged to comply with international law. Such compliance is in accordance with the values the UK applies internally.

Second, if the international law framework fails, then the beneficiaries will be states such as Russia, states that seek to profit from the undermining of the international legal framework. That is why – he says – the stance of the pseudo-realists in practice gives succour to Russia.

Third, “international law is a key vehicle by which states can both pursue their strategic interests and at the same time give effect to the norms and values that they hold dear.”. Here the Attorney General is speaking not simply of human rights instruments but also of other areas of international law such as defence treaties.

Fourth, the UK’s international obligations are not onerous but manifestly in its interests. Here he re-iterates the range of areas (defence, trade, procurement, etc.) where the UK benefits as a leader in the “rules-based international order”.

There is considerable room for debate as to whether the UK lives up to these reasons. However, the first reason in particular sets a yardstick (there can be no pick and mix approach to compliance with international law), while the third allows scope to develop the argument that human rights instruments such as the ECHR articulate and advance UK state power (for the reasons given above in the discussion of pseudo-realism). The fourth is a call to the UK to lead globally in upholding international law. Looked at in realist terms, that last reason can be defended (as can the first three reasons) on the basis that it is in the UK’s interests as a medium-sized power, located in the European region, and facing the particular challenges before it, so to act. It does not need further idealist or ethical support to hold up, thought it may be buttressed with such arguments.

Looked at in realist terms, the only states that may profit from breaking international law as it applies to the society of states are those states that seek to dominate their international environment beyond the scope permitted by international law and which possess the capacity to do so, as well as those states that perceive a crisis to their existence such that they break international in the exercise of sovereign power on that basis that it is perceived as necessary to do so. The UK falls into neither category and the Attorney General is correct to deprecate the arguments of the pseudo-realists accordingly.

The limits of progressive realism
The Attorney General sets the standard for progressive realism: “[w]e are Progressive Realists because painstakingly upholding and strengthening the rules that enshrine respect for human dignity, accountability for breaches of international humanitarian law, fair rules permitting free trade, protections of our environment and defence pacts that protect our nation— is not restraining ourselves but pursuing our national interest…” Thus, under the current government, the central issue for debate will not be whether the UK should break an international treaty commitment or whether it should resile from such a commitment but rather it will be whether the UK is interpreting and applying its international treaty commitments correctly.

Many of the policy choices advanced as examples of progressive realism, such as that in relation to border policy, are and will be hotly debated and contested. Indeed, many of the particular premises underpinning aspects of that policy are not accepted universally in the wider UK legal and political community, not least when measured against international treaty commitments concerning human rights. The same is true as regards arms exports and humanitarian law standards. Such disagreement is to be expected and the debate as to the course of progressive realism and the particular UK foreign policy choices that have been made is part of the democratic process.

Nonetheless, the articulation of a foreign policy approach that recommits to the general application of international law without exception, while underscoring the direct, concrete, benefit to the UK of such an approach, is to be welcomed. Moreover, insofar as it contains the argument that UK participation in human rights treaties and systems is not simply a matter of advancing ethical values but of the use of UK power to create a more benign international environment for the UK and its inhabitants, it is to be particularly welcomed.