The main provisions of the European Communities Act for sovereignty purposes are as follows.

The ECA 1972, s 2(1) gives direct effect to Community law within the UK. It provides that: 'All such rights, powers, liabilities, obligations and restrictions from time to time created or arising by or under the Treaties, and all such remedies and procedures from time to time provided for by or under the Treaties, as in accordance with the Treaties are without further enactment to be given legal effect or used in the United Kingdom, shall be recognised and available in law, and be enforced, allowed, and followed accordingly; and the expression "enforceable Community right" and similar expressions shall be read as referring to one to which this subsection applies.'

The ECA 1972, s 2(4) provides that: '… any Act passed or to be passed shall be construed and have effect [subject to directly applicable Community Law].'

According to the ECA 1972, s 3(1), questions of law relating to the Community shall be determined according to the principles and decisions laid down by the European Court of Justice (ECJ).

Since the UK became a member of the EC/EU, there have been a number of interpretations as to the effect of European Law on parliamentary sovereignty.