Chapter 5 begins by briefly looking at the British Slave Trade Act of 1807, which also marked the beginning of the Royal Navy’s operations off the coast of West Africa. It concentrates on the developments that led from a national ban and its unilateral military enforcement by the United Kingdom to its international and multilateral implementation. A crucial turning point is marked by the Congress of Vienna, at which the political pressure built up by the abolitionists was so great that, for the first time, the proscription of the slave trade was jointly proclaimed and enshrined as a humanitarian norm in international law. This interdict then formed the point of reference for a series of highly controversial negotiations between the European states to decide on collective measures to be taken against this border-crossing problem. A bilateral approach between Britain and the continental powers finally resulted in a mechanism for implementation to be set up, which consisted of a previously unheard of combination of military and legal measures and which, in the shape of the Mixed Commissions for the Abolition of the Slave Trade, produced one of the first forms of international jurisdiction.