The vast majority of UK law originates from the European Union. It is estimated that 80% of law currently in action in the UK has derived from the EU, and therefore a British withdrawal would mean huge changes for the UK legislation system.
The signing of the Treaty of Lisbon resulted in a mechanism by which states could withdraw from the EU, as pre-2007, this was next to impossible. This treaty amended the EU founding treaties.
As the UK legislation is heavily derived from the EU, leaving the EU would have a huge effect on the system. These impacts would begin with the ceasing of the Treaties (TEU and TFEU), which would include as part of those, the fundamental freedoms (movement of labour, capital and goods/services). This would result in the protection of UK citizens living in or intending to live in an EU state vanishing. Residents of the UK will require visas to visit member states, and the rights that derive from the fundamental freedoms and apply in UK courts will be taken from UK citizens.
The whole efficiency of judicial rulings, or case law, would have to be revisited. These were decided and confirmed after a preliminary reference procedure. These case laws are sometimes referred to the Court of Justice of the EU of a question regarding EU law, and this clearly could not occur following a British withdrawal.
Currently, national legislation in the UK is adopted to obey the EU Directives. This could potentially be repealed or amended, depending on which is more beneficial to the UK. Unfortunately, assessing the costs and benefits of keeping those provisions will be a huge and difficult task (given the great number of measures and the methods of how the UK has handled the EU Directive). Arguably, the Financial Regulation and Company Law would be the highest priority measures to be revised. But even these would take years, as revising them would simply add huge amounts of pressure to the workload of the UK Departments and Parliament. Taking on new measures and changing old laws just is not feasible given the current circumstances.
This article was contributed by the LawNinja.