This Master's Thesis focuses on the regulatory framework in Austria and the European Union with regard to provision of flexibility in electricity networks. It further contributes to an Austrian lighthouse project on the integration of Loads and Electric storage systems into Advanced Flexibility Schemes for low-voltage networks (LEAFS). Flexibility sources, such as distributed generation, storage systems and demand response allow not only to incorporate more energy generated from renewable sources into the grid but also to ensure its stability and carry benefits for grid operators, market actors and consumers alike. Multiple grid and market services could be provided by distributed sources of flexibility on par with centralized flexible generators. Flexible components thus lie at the intersection of the electricity network and the market and can potentially be owned and operated by various actors in the evolving system. This research studies possible deployment scenarios of sources of flexibility in the national and European regulatory environment. It identifies existing gaps and inefficiencies with the help of legal and policy documents, a survey of expert opinion and best practices retrieved from relevant European projects, leading the way to a comprehensive gap analysis. Results show that despite positive developments in the related EU and Austrian policy, current regulatory framework is still characterized by a number of grey areas with respect of the status and treatment of distributed flexible resources while different actors in the electricity systems lack adequate incentives for their deployment. This Master's Thesis thus analyzes the identified critical points and elaborates possible action plans needed in order to streamline the regulation of flexibility, improve incentives and reduce system complexity in ways consistent with the goals of the EU energy policy.