Much of UK law derives from EU legislation, or is inspired by it.
Critics of EU institutions sometimes speak of "Brussels diktat", while supporters of integration argue that having common rules makes life easier for EU citizens.
Here Timothy Jones, a lawyer at the UK Treasury Solicitor's Department, explains how EU - or "Community" - legislation becomes part of UK law. His analysis is not the official position of the UK government.
Does EU law go too far - for example, by dictating the acceptable dimensions of fruit?
We frequently hear about laws coming from Brussels, like some distant imperial ruler legislating for its colonial subjects. In fact, those laws come from gatherings of member states' representatives - including UK government ministers and the MEPs we vote for.
The European Commission is in charge of drafting EU legislation
Perhaps this sense of dislocation from "Europe" is reinforced by the EU's complex and often misunderstood law-making process.
In that respect, Commission Regulation (EC) 2257/94 has a lot to answer for. In particular Annex I, which requires that bananas be "free from malformation or abnormal curvature of the fingers". In short, it means that bananas must be straight.
I retained the mistaken view through childhood that European legislation was preoccupied by minutiae, and thrust upon us by a complex bureaucratic cabal intent on eliminating national identity.
Rather than deal in minutiae, though, European law is made to support one or other of the objectives set down in the EC Treaty, such as promoting a common market between member states or preserving, protecting and improving the quality of the environment.
The Community must also have the power to legislate in a particular area - again ascertained by reference to the EC Treaty.
Can member states simply ignore EU legislation?
No, but they can certainly challenge it. If there are doubts about the Community's legitimacy for making a particular piece of legislation (for instance because it does not meet a Treaty objective, or is not based on a power ascribed by the Treaty) then national courts can suspend the domestic measures which implement it.
Rarely, the Treaty itself might be amended. In such cases, the UK will normally make the amendment by an Act of Parliament or by an Order of the Privy Council, made under a power of that Act.
Member states must also look out for developments in the domestic and European courts, which might give rise to new interpretations of Community law, and thus require previous measures to be further amended.
So how is EU legislation adopted?
Most European law-making is done by means of "secondary" legislation (secondary, that is, to the Treaty).
It generally begins with the European Commission making a proposal, often in response to the invitation of a particular member state. The European Council - the grouping of EU governments - and the European Parliament will then debate and amend before adopting it.
How the legislation then impacts upon domestic law will vary according to the form it takes and on how the member state chooses to implement it.
In practice, member states have two key roles in the European legislative process - advising on the form that the proposal will take, and then ensuring it is given effect domestically.
Firstly, central government departments will liaise closely with their permanent representatives in Brussels, to ensure that the legislation being proposed chimes with their own national interests as closely as possible.
Negotiations between 27 different countries, each with its own priorities, policies and domestic legal systems, can be long and drawn out.
In the UK's case, departmental policy officials must assess the impact of the proposal on the UK, and consider whether it is actually the best way of achieving the Commission's original policy objective.
It may be, for instance, that action would be more appropriate at a national or local level. Whitehall departments must then work closely with UKRep (the UK Permanent Representation to the EU), often via COLA (the Cabinet Office Legal Advisers team within the Treasury Solicitor's Department). It is their job to co-ordinate EU law issues for the government. Often they invite lawyers from different departments to large roundtable meetings designed to reach a unified position.
Member states are responsible for ensuring that their national legislation is consistent with European law. Where it is not, they must amend existing provisions, and introduce such new law as necessary.
Ultimately, individuals can be bound by either national or European law. Food safety, for example, comes under EU law, whereas most criminal law is national.
What is the difference between EU directives and regulations?
Directives are addressed to member states rather than their citizens, and are therefore only legally binding upon the states themselves.
Under the process known as "transposition" the directive sets the framework but the practical details of implementation are left for the member states to decide.
By contrast, regulations have "general application". That means they are binding on individuals and effectively form part of domestic law as soon as they are made. It is generally only necessary to amend existing national provisions that are inconsistent with regulations, rather than make new legislation altogether.
Is it difficult to turn EU directives into national law?
Yes, transposing a directive is often complicated by the language of the European legislation.
With so many different tongues spoken within the EU, it is sometimes difficult to identify a definitive reading of the Commission's intention, and there may be subtle variations between different language texts. It might be that the European text is relatively ambiguous as a result, so the government must decide whether to simply restate the English-language European text - to avoid any risk of having failed to reflect its meaning - or whether to attempt a more precise interpretation.
European law emerges out of policy areas that are delineated differently to those described by departmental portfolios at domestic level.
The UK government has to comprehensively consult stakeholders and consider which areas of law might be affected. A balance has to be struck between giving effect to the European legislation and maintaining the effect of pre-existing national legislation where possible.
Does the UK government embellish, or "gold-plate", EU legislation?
In 2005 the government asked Lord Davidson QC to examine the UK's European-sourced legislation, to identify areas where there might be an unnecessary regulatory burden.
His report concluded that there was some room for improvement, so further guidance was issued to departments, emphasising the need to ensure that any new legislation did not encumber its users any more than was necessary.
It is UK government policy not to go beyond the minimum requirements of European directives unless there are exceptional circumstances - as justified by a cost-benefit analysis and extensive consultation with stakeholders.
What penalties can the EU impose if member states defy EU law?
Unlike domestic legislation, there is a real and binding imperative to meet the Commission's time scales for implementation.
So even before the measure is adopted, departments will have started thinking about a project plan for implementation, including key dates by which consultations must have been completed.
Failure to transpose directives within the Commission's deadline will give rise to possible actions against the government, before both national and European courts.
The Commission can bring infraction proceedings before the European Court of Justice under Article 226 of the Treaty. In this respect the UK has a very strong record. Indeed, according to the most recent figures available, for 2007, the UK was the only member state to see more infractions dismissed than declared.
If a member state fails to correct the breach the Commission may take the additional (and rare) step of bringing Article 228 proceedings. That means a member state might either be charged a lump sum or fined on an ongoing basis until the defect is put right, or possibly both.
So far, the UK has not been subject to such an action, and has in fact intervened in support of the Commission's enforcement.