The general principles of EU law
The general principles are the fundamental legal principles governing the way in which the EU operates. They are a part of EU law which the EU institutions and member states must comply with. The general principles are applied by the CJEU and domestic courts when determining the lawfulness of legislative and administrative measures within the scope of EU law, and they are also an aid to interpretation of EU law. Examples of the general principles include proportionality1, non-retroactivity (i.e. that the retroactive effect of EU law is, in principle, prohibited), fundamental rights2, equivalence3 and effectiveness.4
	UK laws that are within the scope of EU law and EU legislation (such as directives) that do not comply with the general principles can be challenged and disapplied. Administrative actions within the scope of EU law must also comply with the general principles.