The EU network codes and guidelines for electricity, first introduced in the Third Energy Package, are designed to enable the implementation of an EU internal electricity market. These codes and guidelines aim to regulate the grid operation and trading rules which govern all cross-border electricity market transactions and system operations in the internal energy market. However, these rules present complex legal challenges, in particular the terms, conditions, and methodologies that are attached to the implementation of the guidelines. This text is intended as an introductory guide to some of the legal issues surrounding the drafting, implementation and amendment procedures of these network codes and guidelines.