Current Affairs · · Prelims · Polity

Cardiff MoU: a joint call for constitutional change in the UK

On 14 September 2026, leaders of the SNP, Plaid Cymru and Sinn Féin agreed a Cardiff memorandum urging the UK government to prepare for constitutional change. Their aims and legal routes differ: Scottish and Welsh independence have no automatic referendum route, while Northern Ireland has a statutory border-poll mechanism. The memorandum itself changes no law.

Event date:

REq1
  1. Context1 / 5

    On 14 September 2026, four party leaders agreed a memorandum of understanding in Cardiff: John Swinney of the Scottish National Party (SNP), Rhun ap Iorwerth of Plaid Cymru, and Mary Lou McDonald and Michelle O'Neill of Sinn Féin. They signed in their party roles, although Swinney, ap Iorwerth and O'Neill also head devolved governments.

    The memorandum asks the UK government to prepare for, plan and facilitate constitutional change in each jurisdiction. It expresses a shared political claim to self-determination while acknowledging that the parties have different goals and timetables. An agreement among parties cannot itself change constitutional powers or grant a referendum.

  2. Key highlights2 / 5

    Three goals: The SNP seeks Scottish independence, Plaid Cymru seeks Welsh independence, and Sinn Féin seeks Irish reunification. The last goal is a united Ireland, not an independent Northern Ireland.

    Two Cardiff documents: Scotland's and Wales's governments also signed a separate Cardiff Agreement on cooperation. Its subjects include child poverty, the cost of living, fiscal arrangements, climate and international engagement. That bilateral government agreement is distinct from the three-party memorandum.

    Earlier votes frame the debate:

    VoteYearResult
    Wales: create an assembly199750.3% Yes
    Wales: extend law-making powers201163.5% Yes
    Scotland: independence201455.3% No; 44.7% Yes; 84.6% turnout
    EU membership: Scotland2016About 62% Remain
    EU membership: Northern Ireland2016About 56% Remain
    EU membership: Wales2016Leave majority

    The two Welsh votes asked different questions, so their Yes shares cannot be read as a trend in support for independence.

  3. Key concepts3 / 5
    1. Devolution and federalism

    UK law transfers different powers to Scotland, Wales and Northern Ireland, while Parliament at Westminster retains legal sovereignty. That is asymmetric devolution. In a federation such as India, the constitution itself allocates powers between the Union and States.

    1. A Scottish referendum

    The UK Supreme Court held in 2022 that Scotland's Parliament cannot legislate for an independence referendum on its own. The Union and the UK Parliament are reserved matters. A lawful route therefore needs action at UK level.

    1. Northern Ireland's consent rule

    Under the 1998 settlement, Northern Ireland remains in the UK unless a majority votes otherwise. The Northern Ireland Act requires the Secretary of State to call a border poll if a majority for a united Ireland appears likely. A further poll cannot be held within seven years of an earlier one.

    1. Self-determination and legal authority

    A political demand for a vote does not by itself give a devolved body authority to call one. The legal route differs among the three nations.

  4. Note4 / 5

    Three nations, different constitutional routes

    NationParty aimCurrent route to a vote
    ScotlandSNP seeks independenceRequires a lawful UK-level route; no unilateral Scottish Parliament power
    WalesPlaid Cymru seeks independenceNo standing independence referendum mechanism
    Northern IrelandSinn Féin seeks Irish reunificationBorder poll under the 1998 consent framework

    The memorandum links these campaigns to Brexit and a preference for a European future. The 2016 EU vote was uneven: Scotland and Northern Ireland voted Remain, while Wales voted Leave. EU membership after any constitutional change would require its own legal and political process.

    Questions of currency, debt, public spending, taxation and trade would also have to be addressed. Northern Ireland's path must follow the consent arrangements in its 1998 settlement.

  5. Note5 / 5

    PSIR lens: can devolution accommodate nationalism?

    ReadingWhat it points to
    AccommodationDevolved institutions and Northern Ireland's power-sharing framework provide ways to govern within the UK
    Continuing tensionNationalist parties can gain governing mandates while Westminster keeps legal authority over the Union

    Both readings matter. Devolution distributes day-to-day power, but the route to changing sovereignty remains contested. The three parties also seek different outcomes, so one legal formula does not fit all.

    India offers a comparison, not an identical model. Articles 371 and 371A–J and the Sixth Schedule provide differentiated arrangements within a written Constitution. The comparison helps separate political representation, allocation of powers and the legal authority to alter a constitutional settlement.

Sources

Syllabus

PaperSubjectSub-topic
PrelimsPolityComparative constitutions, devolution and the Good Friday Agreement
GS2PolityComparison of India's constitutional scheme with that of other countries
PSIRPolitySovereignty, nationalism, federalism and comparative politics

Topics

International Relations and Current AffairsCentre-State RelationsMiscellaneous PolitySystems of Government

Practice questions

  1. With reference to the UK's constitutional structure, consider these statements: 1. Devolution gives Scotland, Wales and Northern Ireland different powers. 2. The UK Parliament retains legal authority to legislate for the UK. 3. The UK is a federation whose single codified constitution entrenches a division of powers. Which are correct?

    1. 1 and 2 only
    2. 1 and 3 only
    3. 2 and 3 only
    4. 1, 2 and 3
    Show answer

    Answer: A. Statements 1 and 2 are correct. The UK's devolved arrangements differ, but parliamentary sovereignty remains at Westminster. Statement 3 is wrong: the UK has no single codified federal constitution.

    Difficulty: medium · statement

  2. Consider these statements about Northern Ireland's 1998 settlement: 1. It provides for power sharing between communities. 2. A change in Northern Ireland's constitutional status requires majority consent there. 3. It created the Scottish Parliament. Which are correct?

    1. 1 and 2 only
    2. 2 and 3 only
    3. 1 and 3 only
    4. 1, 2 and 3
    Show answer

    Answer: A. Statements 1 and 2 are correct. The 1998 settlement created Northern Ireland's power-sharing framework and consent principle. Scotland's Parliament arose from a separate devolution process.

    Difficulty: medium · statement

  3. Consider these statements about the 2026 Cardiff memorandum: 1. Leaders of the SNP, Plaid Cymru and Sinn Féin agreed it on 14 September 2026. 2. It grants Scotland and Wales a legal right to hold independence referendums. 3. It does not itself create a new referendum route. Which are correct?

    1. 1 and 2 only
    2. 1 and 3 only
    3. 2 and 3 only
    4. 1, 2 and 3
    Show answer

    Answer: B. Statements 1 and 3 are correct. The memorandum is a political agreement among parties; it does not transfer constitutional powers or authorise a referendum.

    Difficulty: easy · statement

Mains practice

Answer-writing practice on this article. Attempt it first, then open the hints.

  1. GS2 · 250 words

    The Cardiff memorandum highlights tensions in the UK's asymmetric constitutional order. Examine with reference to devolution and parliamentary sovereignty.

    Show hints
    1. Define asymmetric devolution.
    2. Separate the parties' three constitutional aims.
    3. Explain Westminster's legal authority and the Scottish court ruling.
    4. Describe Northern Ireland's consent and border-poll route.
    5. Assess the uneven effect of Brexit on the argument.
  2. PSIR · 250 words

    Compare the UK's asymmetric devolution with India's asymmetric federal arrangements. Can constitutional asymmetry accommodate sub-national nationalism?

    Show hints
    1. Distinguish UK parliamentary sovereignty from India's written allocation of powers.
    2. Use Articles 371 and 371A–J and the Sixth Schedule as examples.
    3. Discuss representation, fiscal capacity and legal authority.
    4. Explain different nationalist aims and legal routes.
    5. Conclude with the conditions under which asymmetry can endure.