The network codes (sometimes adopted as network guidelines) issued by the European Commission comprise a comprehensive set of regulations governing the electricity sector in the EU. They define and harmonise numerous regulations in the areas of market integration (market and trading codes), grid system operation (system operation codes) and grid connection (connection codes) and thus create the basis for an efficient, integrated internal electricity market across Europe. As legally binding EU regulations, the network codes are directly applicable in all EU member states. They contain numerous obligations for transmission system operators and other market participants that must be implemented within clearly defined periods. Implementation of the network codes therefore requires comprehensive alliances between all participating actors at both national and international level.