The EU treaties are the highest level of EU law. They define where the EU is permitted to act, to what extent and how. They also contain a mixture of procedural rules for how the EU operates and substantive rules, such as free movement rights for EU citizens. The EU treaties also set out subject areas in which the EU can make more specific laws: this is known as the EU’s ‘competence’.

High

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/604516/Great_repeal_bill_white_paper_accessible.pdf

Annex A, A.5