Short answer
The UK Parliament remains legally able to legislate for every part of the United Kingdom. In practice, the Scotland Act 1998, Government of Wales Act 2006 and Northern Ireland Act 1998 allocate broad fields to elected devolved legislatures and governments. Measures outside their statutory competence are not law, and devolved executives must also remain within devolved competence.
Scotland and Wales now use reserved-powers models: their legislatures may generally legislate unless a matter is reserved or another statutory restriction applies. Northern Ireland distinguishes transferred, reserved and excepted matters, within a power-sharing settlement. Typical devolved fields include health, education, local government, housing and many aspects of transport, environment and justice, but the precise allocation and exceptions differ. Defence, foreign affairs, immigration and central macroeconomic matters are generally reserved; justice is devolved in Scotland and Northern Ireland but not in the same way in Wales.
The Sewel convention says Westminster will not normally legislate on devolved matters without consent, but courts do not enforce it as a legal veto. UK-wide legislation, internal-market rules, international obligations, finance and ministerial intervention powers can affect the practical room for divergence. Every proposal therefore needs a statute-and-schedule analysis of purpose, effect, territory, protected enactments, rights and executive function—not a generic subject label.
Westminster retains legal sovereignty
Devolution transfers power without creating a federal constitution. The UK Parliament can enact law for Scotland, Wales and Northern Ireland, amend the devolution settlements and confer, share or withdraw functions. The states this expressly while recognising the permanence of the Scottish institutions; equivalent permanence provisions exist for Wales.
The UK Government exercises functions in reserved fields, implements Westminster legislation and uses prerogative powers such as treaty-making. Ministers need statutory or prerogative authority: sovereignty belongs to the Crown in Parliament, not to the executive. A UK department cannot assume power over a devolved service merely because its policy has UK-wide importance.
England has no separate national legislature or government. Westminster and UK ministers perform both UK-wide and England-only functions, so one Act may mix territorial scopes.
Scotland: everything not reserved, subject to statutory limits
Under sections 28 and 29 and Schedules 4 and 5 of the Scotland Act, the Scottish Parliament may legislate for Scotland unless a provision:
- forms part of another territory's law or confers functions otherwise than in or as regards Scotland;
- relates to a reserved matter;
- breaches restrictions on modifying protected enactments;
- is incompatible with Convention rights or specified Withdrawal Agreement constraints; or
- interferes with the Lord Advocate's protected role.
Schedule 5 reserves matters such as the constitution, defence, foreign affairs, immigration, much fiscal and monetary policy, many aspects of employment and social security, and specified regulation. Exceptions return particular topics to Scottish competence. Health, education, local government, housing, agriculture, environment, planning, criminal and civil justice and policing are principally devolved, but cross-border and reservation-specific qualifications must be checked.
Section 53 broadly transferred pre-existing ministerial functions within devolved competence to the Scottish Ministers. Later statutes add, share or reserve functions. Executive competence generally tracks what the Scottish Parliament could legislate for, but the exact function and its conferring instrument remain decisive.
In the , the Supreme Court held that a proposed referendum Bill related to the reserved Union and UK Parliament. Section 29 provides:
“An Act of the Scottish Parliament is not law so far as any provision of the Act is outside the legislative competence”
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Courts assess a provision's purpose by reference to its effect in all the circumstances. A measure can “relate to” a reservation without directly amending reserved law.
Wales: a reserved-powers model with a different reservation map
The , substantially revised by the Wales Acts, gives the Senedd a reserved-powers model. Section 108A and Schedule 7A ask whether a provision extends beyond Wales, relates to a reserved matter, breaches protected-enactment restrictions or conflicts with Convention rights or other stated limits.
Health, education, local government, housing, planning, agriculture, culture, environment and much transport policy are devolved. But the Welsh reservation list differs from Scotland's. Policing, criminal justice, prisons and most courts remain reserved, notwithstanding devolved powers over prevention, services and tribunals in particular fields. Some tax powers are devolved within statutory limits.
Welsh Ministers exercise functions expressly conferred or transferred to them and executive ministerial functions within devolved competence under the current Act. Some powers are concurrent or joint with UK ministers. A Senedd Act cannot create executive competence in a field that the legislature itself could not enter.
Older decisions under Wales's former conferred-powers model, including the , must not replace the current section 108A test.
Northern Ireland: transferred, reserved and excepted matters plus power sharing
The implements the constitutional settlement arising from the Belfast/Good Friday Agreement. Matters not listed as excepted or reserved are generally transferred. Excepted matters in Schedule 2—such as the Crown, Parliament, defence, nationality and core external affairs—are not expected to devolve under the ordinary mechanism. Reserved matters in Schedule 3 may be transferred by Order in Council; policing and justice were transferred in 2010, subject to specific arrangements.
The Assembly cannot legislate incompatibly with Convention rights, specified EU Withdrawal Agreement obligations or other competence restrictions. In the , the Supreme Court assessed Convention proportionality because incompatible legislation would fall outside competence; it upheld the provision.
Executive authority is exercised through the First Minister and deputy First Minister, Executive Committee and Northern Ireland departments. Ministerial appointments, significant decisions and some Assembly votes are governed by cross-community and power-sharing rules. Departmental competence, Executive referral duties and periods when institutions are not functioning can be as important as whether the subject is transferred.
Northern Ireland also has distinct constraints under the Windsor Framework. Specified EU rules may continue to apply, and democratic-consent and Stormont Brake mechanisms operate within their own conditions. This is not captured by the general reserved/transferred classification alone.
Sewel coordinates overlapping sovereignty and autonomy
The Sewel convention is reflected in the devolution statutes: Westminster will not normally legislate with regard to devolved matters without the relevant legislature's consent. Legislative consent motions also commonly address provisions that alter devolved executive competence.
In , the Supreme Court held that statutory recognition did not convert Sewel into a judicially enforceable rule:
“the policing of its scope and the manner of its operation does not lie within the constitutional remit of the judiciary”
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Refusal of consent can be constitutionally and politically serious, but it does not legally invalidate an otherwise valid Westminster Act. “Not normally” is assessed politically, and Parliament may legislate despite refusal.
Common frameworks, the internal market and international obligations
After Brexit, governments use common frameworks to coordinate regulation formerly shaped by EU law. These arrangements guide cooperation and dispute resolution but ordinarily do not themselves change statutory competence.
The overlays market-access rules on devolved regulation. Mutual recognition can permit goods or services compliant in one UK part to circulate in another; non-discrimination rules restrict certain differential burdens. A devolved rule may therefore be within legislative competence yet have reduced practical effect on incoming products. Statutory exclusions, amendments and common-framework interaction must be checked for the sector and date.
International relations and treaty-making are reserved, but implementing obligations often touches devolved matters. The UK remains internationally responsible; devolved governments may implement within competence, while settlement statutes give UK ministers intervention or direction powers in defined circumstances. Those powers are legally reviewable and should not be confused with a general policy override.
Finance and taxation do not map perfectly onto subject competence
Block grants sit alongside devolved taxes, borrowing powers and assigned revenues. The Barnett formula is a funding convention, not a competence rule. Tax bases, collection and borrowing ceilings remain statutory.
A legislature's power to regulate a service does not necessarily include unlimited taxation, borrowing or public expenditure. Conversely, UK spending power does not automatically transfer regulatory control over the funded devolved activity.
A practical competence analysis
For each proposed provision or executive act:
- identify the institution, territory and exact legal source of power;
- define the provision's purpose and practical effects;
- test every relevant reservation, exception and protected enactment;
- check Convention rights, Withdrawal Agreement/Windsor Framework and territorial limits;
- identify whether executive power is transferred, concurrent, joint or retained;
- assess legislative consent, consultation and intergovernmental mechanisms separately from legal validity; and
- check internal-market, finance, subsidy and international-obligation overlays.
Conclusion
UK devolution combines continuing Westminster sovereignty with legally enforceable grants of autonomous legislative and executive power. Scotland, Wales and Northern Ireland each have a different statutory map, and subject labels are only a starting point. Courts enforce competence limits; Sewel is politically rather than judicially enforced; and UK-wide statutes can overlay valid devolved policy. Sound analysis therefore reads the current settlement Act, schedules, amendments and function-conferring legislation provision by provision, then separates legal competence from consent, funding and intergovernmental politics.
Sources
This article provides general legal information, not advice for a specific matter. Laws, facts and procedural deadlines may change the result. Follow the linked primary sources and obtain local advice before acting.