The principle of parliamentary sovereignty has been dramatically affected because of Britain's membership of the EU.

In theory, this peculiarity of the British constitution means that Parliamentary supremacy and the primacy of European law in the areas covered by the European Treaties are fundamentally incompatible.

European legislation is initiated almost exclusively by the European Commission with which the UK Parliament has no formal relationship and over which it has no direct control. In these circumstances there are a number of procedural and other problems for Parliament at Westminster:

First, there is the volume of European legislation which is hard for the House of Commons to deal with properly within the constraints of an already congested legislative timetable. Secondly, a serious problem for Parliament, which has arisen since the 1986 Single European Act - extended in the 1997 Treaty of Amsterdam - is that the use of qualified majority voting in the Council of Ministers has reduced the areas in which any member state can veto decisions at European level.  

Sovereignty and the Human Rights Act

The Labour Government incorporated the European Convention of Human Rights into UK law as the Human Rights Act in in October 2000. Labour’s Bill makes it unlawful for public bodies (including government departments, agencies, the police, prison officers, privatised utilities and the armed forces) to exercise their powers in ways which are incompatible with the ECHR. Citizens will be able to appeal to the principles enshrined in the ECHR in any court in Britain. Courts will be able to quash actions of public bodies and to grant compensation to victims of abuse of power.  Acts of Parliament are to be interpreted in ways which are compatible with the ECHR (ie if there is ambiguity or vagueness, the ECHR will be used to interpret an Act in ways which make it fit the principles of the convention). If parliament passes legislation  which the higher courts believe is not compatible with the ECHR, they can issue a formal declaration to that effect. The courts will not have the power to veto such an act as unlawful, but the Labour White Paper states that such a declaration will ‘almost certainly’ prompt a government to change the law. So, as envisaged by the current government, parliamentary sovereignty will remain intact but the ECHR will have both legal and moral force in restricting the actions of parliament and government.

Sovereignty and Devolution 

• Devolution has taken away more power from the Westminster Parliament.
• A unitary state, is one where there is one central law-making body, and one executive or government. The implication is that all parts of the state have the same laws, which are administered and implemented by the same institutions. Britain has usually been seen as a unitary state because of the principle of parliamentary sovereignty, i.e. the location of supreme legal power in the UK is the Westminster parliament.
• However, the UK has always been best described as a union state, where different regions are often treated differently and where some degree of regional self-government remains. For example, Scotland retained its own legal system after the union of 1707.
• Devolution is ‘the delegation of central government powers to subordinate units, these powers being exercised with some degree of autonomy though with ultimate power remaining with central government.’ 
• So, ‘Devolution is a process by which Parliament transfers its powers without relinquishing its supremacy’ (both quotes from Vernon Bogdanor). For example, Northern Ireland’s virtual autonomy within the UK was ended when the British government restored direct rule in 1972, abolishing the Northern Ireland parliament (Stormont). 
• Devolution produces three questions about parliamentary sovereignty:

• Devolution does limit parliamentary sovereignty because the Westminster Parliament is allowing other bodies – like the Scottish Parliament – make law. For example, smacking small children and hunting with dogs are illegal in Scotland but not the rest of the UK.
• The idea that power can be taken back by the Westminster parliament is true in theory but very unlikely in practice.
• The power of the Westminster Parliament is likely to continue to be eroded – for example, as English regions acquire elected assemblies.

Conclusion 

• The concept of parliamentary sovereignty is rather misleading as it indicates that there is one source of legal and political power. In reality:

• ‘Parliament’  is not the real force in UK politics – the executive or government is.
• There are many practical limitations on what laws a parliament can pass
• Membership of the EU has had great impact on the legal concept of sovereignty because in many ways legal sovereignty has been voluntarily passed to the EU institutions
• The HRA has preserved the concept of parliamentary sovereignty in theory, but in practice it has restricted the powers of parliament and given citizens and the courts power to challenge parliament 
• Devolution has significantly restricted the powers of the Westminster Parliament.