More than half of world-wide e-mail traffic – an estimated total of several billion e-mails per day – consists of spam. This is becoming a considerable disturbance to telecommunications. Spam is also closely related to other kinds of cyber crime as it possibly contains malicious software or is pursuing some kind of fraudulent aim, such as phishing. Besides technical and organizational measures, many countries have introduced anti-spam legislation. However, today's world-wide legislative coverage of spam is heterogeneous, and its effectiveness is controversially discussed. This article describes important parameters by which anti-spam legislation can vary and gives an overview and analysis of world-wide anti-spam legislation, including the European Directive 2002/58/EC, the U.S. CANSPAM Act of 2003, and international cooperation, such as the London Action Plan. The article then proceeds to discuss the effectiveness of current laws, and it identifies problems resulting from the fact that an international phenomenon is being addressed by national legislation. Finally, the article presents suggestions for overcoming some of these problems.