Currently, EU law forms part of the UK's domestic legal framework, and primary legislation that fails to comply with it can be disapplied. The UK courts also apply EU legal principles (such as proportionality and legal certainty) when considering EU law.
The proposed Great Repeal Bill (and Labour's alternative) will incorporate all EU laws that apply at the point of Brexit into the UK's domestic legal framework. However, some elements of EU law - such as governing principles, institutional arrangements and decision-making processes - are not easily accommodated by a 'cut and paste' approach.
Changes will be required to the body of EU law that we incorporate to ensure that it functions effectively after Brexit. The nature and extent of those changes will also depend on the outcome of negotiations with the 27 continuing EU members, creating a series of late-stage dependencies. These issues create a huge task for government lawyers and a consequent opportunity for trade associations and representative bodies to assist by identifying areas of risk and possible solutions in their sectors.