06 - 05
If you have a single market you must have common rules. If we left the EU but wanted access to the Single Market we would have to go back and abide by many of the same rules as before.
Europe wide regulations allow British firms to trade on equal terms with other companies in the Single Market and maintain seamless supply chains across the continent, without lengthy inspections of for example imported Italian mushrooms at national borders.
Nearly half of UK exports go to the EU. If we are to continue trading with European countries they will still demand compliance with their environmental, safety and other standards. (The Economist December 17, 2016)