Brexit was the withdrawal of the United Kingdom (UK) from the European Union (EU). Following a referendum held in the UK on 23 June 2016, Brexit officially took place at 23:00 GMT on 31 January 2020. The UK, which joined the EU's precursors the European Communities (EC) on 1 January 1973, is the only member state to have withdrawn from the EU. Following Brexit, EU law and the Court of Justice of the European Union no longer have primacy over British laws. The European Union (Withdrawal) Act 2018 retains relevant EU law as domestic law, which the UK can amend or repeal.