Is the United Kingdom rejoining the European Union Customs Union?

By Matthew Parish, Associate Editor

Monday 13 April 2026

The British government’s emerging legislative proposal to permit the use of secondary legislation to align United Kingdom law dynamically with European Union single market standards marks one of the most constitutionally and economically significant developments in post-Brexit Britain. It represents not merely a technical adjustment in regulatory practice but a profound recalibration of the United Kingdom’s political economy, her constitutional doctrine of parliamentary sovereignty, and her geopolitical positioning in an increasingly unstable international system.

At the centre of this proposal lies the concept of “dynamic alignment” — a mechanism by which ministers, acting under powers delegated by Parliament, may update domestic law to mirror evolving European Union regulations without the need for fresh primary legislation on each occasion. In constitutional terms this relies upon the well-established distinction between primary legislation — statutes enacted by Parliament — and secondary, or delegated, legislation, typically enacted through statutory instruments under authority granted by an enabling Act. What is novel, however, is the scale and political sensitivity of the subject matter to which these delegated powers would apply: the regulatory architecture of the European single market itself.

The proposal, as advanced by the government of Keir Starmer, would allow ministers to implement regulatory changes in areas such as food standards, emissions trading and electricity markets through secondary legislation — often described by critics as the exercise of “Henry VIII powers”, permitting modification of primary legislation without full parliamentary scrutiny. While the initial enabling Act would require parliamentary approval, subsequent adjustments could be made with limited debate, thereby ensuring that British regulatory standards remain synchronised with those of the European Union as they evolve.

The political logic of this proposal is rooted in a tension that has defined British policy since the referendum of 2016: the desire to retain formal sovereignty while mitigating the economic costs of regulatory divergence from the European Union. The post-Brexit legislative framework — particularly the European Union (Withdrawal) Act 2018 — was designed to sever the direct applicability of European Union law while preserving existing rules as “retained EU law” to ensure continuity. Subsequent legislation, such as the Retained EU Law (Revocation and Reform) Act 2023, sought to reduce or replace this inherited body of law. Yet the economic reality has proven resistant to ideological simplification: divergence from European standards has generated frictions in trade, particularly in sectors subject to stringent regulatory controls.

Dynamic alignment is therefore best understood as a pragmatic compromise. It allows the United Kingdom to retain the formal legal autonomy to choose alignment, while in practice committing to regulatory convergence where economic incentives dictate. Government sources have emphasised that such alignment is a “sovereign decision” intended to reduce burdens on businesses and lower prices rather than a step towards formal re-entry into the European Union’s institutional framework. Nevertheless critics argue that the absence of voting rights over European Union legislation, combined with reduced parliamentary scrutiny at Westminster, creates a democratic deficit: Britain would effectively adopt rules in whose formulation she has no direct participation.

The economic rationale for this shift is compelling. The European Union remains the United Kingdom’s largest trading partner and regulatory divergence imposes non-tariff barriers that are often more economically significant than tariffs themselves. Divergent standards necessitate duplicate certification, customs checks and compliance costs, particularly acute in agri-food trade and manufacturing supply chains. By aligning with European Union sanitary and phytosanitary regulations for example, the United Kingdom could substantially reduce border friction, facilitating smoother trade flows and lowering costs for producers and consumers alike.

Moreover alignment in areas such as emissions trading and electricity markets promises integration into larger, more efficient regulatory and market frameworks. Linkage of emissions trading systems can enhance liquidity and reduce compliance costs for industry, while participation in integrated electricity markets can improve energy security and price stability. Estimates associated with earlier iterations of the “reset” policy suggested multi-billion-pound gains over the long term, reflecting the cumulative benefits of reduced trade frictions and enhanced market access.

Beyond sector-specific gains the broader macroeconomic effect of alignment lies in restoring predictability. Businesses operating across borders prioritise regulatory certainty; the prospect of continual divergence creates investment risk. Dynamic alignment offers a stable and predictable regulatory environment, encouraging both domestic investment and foreign direct investment into the United Kingdom as a platform for access to European markets.

The geopolitical context of this policy shift is equally significant. The original Brexit settlement was negotiated in a period characterised by relative global stability and a political emphasis on national sovereignty. The intervening years have witnessed a marked transformation in the international environment — including renewed great-power competition, conflict in Europe and instability in the Middle East — prompting a reassessment of the United Kingdom’s strategic alliances. Government statements explicitly situate closer alignment with the European Union within this context of “massive conflict” and global uncertainty, emphasising the importance of cooperation in defence, energy and economic policy.

This reflects a broader European trend towards consolidation in the face of external threats. The European Union has increasingly functioned not merely as an economic bloc but as a geopolitical actor, coordinating sanctions, defence industrial policy and energy security. For the United Kingdom remaining outside the regulatory core of this system risks marginalisation. Alignment, even without formal membership, offers a means of re-engagement and influence, albeit indirectly.

The proposal must also be understood as a domestic political manoeuvre. The Labour government faces the dual imperative of demonstrating economic competence while avoiding the political toxicity associated with reversing Brexit outright. Dynamic alignment provides a means of achieving substantive economic reintegration without reopening the constitutional question of membership. It is in effect a policy of functional reintegration without formal accession.

Yet this approach is not without its risks. The use of secondary legislation to implement alignment raises fundamental constitutional questions concerning the balance of power between the executive and Parliament. The United Kingdom’s uncodified constitution relies heavily upon conventions of parliamentary scrutiny and accountability; the extensive use of delegated powers in areas of high political salience may strain these conventions. Critics’ invocation of “Henry VIII powers” is not merely rhetorical: it reflects a genuine concern that the executive may acquire disproportionate authority over the regulatory framework governing large sectors of the economy.

Furthermore dynamic alignment without representation poses a structural dilemma. The United Kingdom would be bound in practice by rules shaped within the European Union’s legislative institutions, yet would lack a formal voice in their development. This asymmetry may be tolerable in narrowly defined sectors, but becomes more problematic as the scope of alignment expands.

The proposed legislation represents a decisive shift in British policy from the post-referendum emphasis on regulatory autonomy towards a more pragmatic recognition of economic interdependence. It reflects an attempt to reconcile sovereignty with globalisation, autonomy with integration, and political symbolism with economic necessity. Whether it succeeds will depend not only upon its economic outcomes but also upon its capacity to sustain democratic legitimacy within the United Kingdom’s constitutional framework.