Brussels will determine which of our legislation matches theirs and so proves our goods are fit for sale in the EU. We will do the same in the other direction. Removal of admin could lead to goods and services being subject to additional customs checks or rejection.It may well take years for the laws to change, but the levels of admin will fall straight away if we leave the EU. Why would Brussels still be involved with ruling us?
The Calais comment was more about people currently choosing to come here, over so called equal EU member states.