This contribution concentrates on the legal aspects of piracy and tries to explain some of the practical problems which modern navies experience in their fight against piracy and maritime violence off Somalia. The UN Law of the Sea Convention of 1982 provides a traditional though largely deficient set of rules for control and countermeasures. Modern legal instruments such as the SUA Convention of 1988 as amended, recent resolutions of the UN Security Council and regional treaties try to fill the loopholes. Against this background the paper discusses e.g. the law of boarding and investigation of suspicious vessels, the arrest and penal prosecution of criminals and the right of self-defence in case of an imminent attack. The international mandates and the national rules of engagement in which the navies operate reflect these ambiguities that result in a loss of momentum. After all piracy is not an act of war, but a crime. In conclusion a political solution on land is indispensable as the navies and coast guards can only fight the symptoms and not the causes of crime and unrest in a failed State.