EU law in the UK legal system
The ECA is the main legislation which gives effect to EU law in the UK and is the legislation which makes EU law supreme over UK law. This reflects the dualist nature of the UK’s constitutional model under which no special status is accorded to treaties, such as the EU treaties; the rights and obligations created by them take effect in domestic law through the legislation enacted to give effect to them. Although EU treaties and judgments of the EU courts provide that certain provisions of the treaties, legal instruments made under them, and judgments of the EU courts have direct application or effect in the domestic law of all of the member states (see above), such EU law is enforceable in the UK only because domestic legislation, and in particular the ECA, makes express provision for this. Thus, the ECA gives effect to the primacy of EU law and Parliament accepted this principle in approving the Act.
	This has been recognised by the courts of the UK. As Lord Bridge noted in his judgment in Factortame1:
	"Under the terms of the Act of 1972 it has always been clear that it was the duty of the United Kingdom court, when delivering final judgment, to override any rule of domestic law found to be in conflict with any directly enforceable rule of Community law."
	The ECA has been recognised by our courts as being a ‘constitutional statute’ that cannot be repealed by implication (see most recently, paragraph 67 of the Supreme Court’s decision in Miller). Express provision is required to repeal it.
	In addition to section 2(1) and section 2(2) mentioned in paragraph 18 above, the key provisions of the ECA are:
Section 1
Provides that certain treaties are ‘EU treaties’, which means that the later provisions of the Act (such as section 2(1) and (2)) apply to the rights and obligations in them. Such treaties include those establishing the EU itself, instruments amending those treaties (such as the Lisbon Treaty in 2007), and accession instruments. The Euratom Treaty is also a treaty which has effect in this way through the provisions of the ECA.
Section 2(3)
Provides that expenditure to meet an obligation to make payments to the EU or to member states under such a treaty can be charged on public funds. Money received under such a treaty must be paid into public funds.
Section 2(4)
Section 2(4) contains two significant elements. Firstly, that the power under section 2(2) includes the power to make such provision as might be made by Act of Parliament. Secondly it also sets out that any enactment passed or to be passed is to be construed and has effect subject to the foregoing provisions of section 2, including section 2(1). This reflects the fact that EU law takes precedence over the laws of member states, as explained in paragraph 62 of these notes.
Section 3(1)
Provides that for the purposes of all UK legal proceedings, the meaning or effect of any of the EU Treaties, or the validity, meaning or effect of EU instruments are to be interpreted in accordance with the principles laid down by, and any relevant decisions of the CJEU.
Section 5
Provides for the charging, etc. of EU customs duty, which is also now the subject of a directly applicable EU Regulation (the Union Customs Code).
Section 6
Concerns the Common Agricultural Policy (CAP) developed under EU law to support the creation of a common market for agricultural products.
Part 2 of Schedule 1
Provides for several defined terms, which by virtue of the Interpretation Act 1978 apply, unless the contrary intention appears, to all domestic legislation, and not just to the ECA.
Paragraph 1A of Schedule 22
Allows secondary legislation to be made that makes ambulatory cross-references to EU instruments - that is, a reference to that instrument as it may be amended from time to time in the future.
	Since 1973 the UK has passed various other pieces of legislation to give effect to the UK’s relationship with the EU. This included primary legislation amending the definition of EU treaties in section 1(2) of the ECA in the light of revisions to the EU Treaties (for example, the European Communities (Amendment) Act 2002 (regarding the Nice Treaty) and the European Union (Amendment) Act 2008) (regarding the Lisbon Treaty). Other primary legislation further amended the definition of EU treaties in section 1(2) of the ECA to include various Acts of Accession (for example, the European Union (Croatian Accession and Irish Protocol) Act 2013).
	The UK is a member of the EEA by virtue of its membership of the EU. Therefore on exit day the UK ceases to participate in the EEA Agreement. The European Economic Area Act 1993 (EEA Act) makes the EEA Agreement one of the "EU treaties" for the purposes of the ECA, which implements the EEA Agreement in UK legislation. Therefore the provisions of the ECA apply to the rights and obligations in the EEA Agreement, so long as the UK is a member of the EU. The EEA Agreement is also implemented domestically through the EEA Act 1993 and other secondary legislation.
	The European Union Act 2011 required that a referendum be held on certain amendments of the TEU or the TFEU. In short, a referendum would be triggered by amendments if these would transfer power or competence from the UK to the EU. The European Union Act 2011 also provides that an Act of Parliament would be required before the UK could agree to a number of other specified decisions provided for in TEU and TFEU.
	The European Union Act 2011 also contains provisions relating to the approval of the transitional protocol on Members of the European Parliament. As the UK withdraws from the EU, this and other legislation governing participation in European Parliamentary elections (namely the European Parliamentary Elections Act 2002 and the European Parliament (Representation) Act 2003) will be redundant and will be repealed, in line with the overall repeal of these Acts (see Schedule 9). Further provision for participation in European parliamentary elections (contained in other legal sources) will be repealed through secondary legislation made using the delegated powers in the Act.
	The European Union Referendum Act 2015 is the legislation that made provision for holding a referendum in the UK and Gibraltar on whether the UK should remain a member of the EU.
	The European Union (Notification of Withdrawal) Act 2017 gave the Prime Minister the legal authority to notify under Article 50 of the TEU.