Dark liquidity sheds light on the global phenomenon of non-transparent securities trading. While economic research is incapable of drawing a clear picture of the harm and benefits of dark liquidity, legislators and regulators in modern capital markets are nevertheless pressed to provide a suitable regulatory framework for it. By using law and economics as well as comparative law methods, this work examines the regulation of dark liquidity in the USA, the EU and Switzerland, highlights the strengths and weaknesses of different approaches and formulates guidelines for effective regulation in practice. The work thus informs government decision-makers, academics and practitioners in capital market law.