Disentangling the UK from over 40 years EU legislation is a huge task that will take years to complete. To overcome this problem, the government is drafting the “Great Repeal Bill”, which will try to simply convert EU laws into domestic legislation, before asking parliament to repeal the 1972 European Communities Act.
Simple as it sounds, there are some tricky legal issues that need to be taken into account. These are descried in a new briefing paper for the House of Commons, a summary of which can be found on the parliament website, as well as a link to the full report (pdf file).
Summary: http://researchbriefings.parliament.uk/ResearchBriefing/Summary/CBP-7793