The Council Regulation (EC) No 139/2004, enacted on 20 January 2004, outlines the framework for controlling concentrations between undertakings to ensure that competition within the European Union's internal market is not distorted. This regulation recasts the previous Regulation (EEC) No 4064/89, adapting it to the evolving market landscape while emphasising the need for a coherent policy that promotes dynamic competition, economic growth, and improved living standards across the Community. Concentrations exceeding specific turnover thresholds that significantly impact competition are subject to scrutiny, with emphasis on a one-stop-shop approach for regulatory clarity.

Moreover, the regulation establishes a cooperative framework among the European Commission and Member States, allowing for effective information sharing and referral mechanisms. It also addresses potential anti-competitive effects resulting from concentrations, including the creation or strengthening of market dominance, while providing guidelines for assessing efficiencies that could mitigate such impacts. The regulatory processes aim to balance market interests and preserve legal certainty without impeding competitive progress.