British legislation forbade ships under British registry to engage in the slave trade, but the restriction was applied generally to all flags and was intended to shut down all traffic in slaves coming out of West African ports. Other countries more or less hesitantly followed the British lead. The United States, for example, also prohibited the slave trade in 1807 (Denmark actually was the first country to declare the trade illegal in 1792). Attitudes changed slowly, however, and not all countries cooperated in controlling the activity of their merchant ships. American ships, for instance, were notorious for evading the prohibition and going unpunished under United States law. It should be noted, moreover, that the abolition movement concentrated on the transatlantic trade for more than five decades before eventually becoming a full-fledged attack on slave trading within Africa itself.
The Royal Navy maintained a prevention squadron to blockade the coast, and a permanent station was established at the Spanish colony of Fernando Po, off the Nigerian coast, with responsibility for patrolling the West African coast. For several decades, as much as one-sixth of all British warships were assigned to this mission, and a squadron was maintained at Fernando Po from 1827 until 1844. Slaves rescued at sea were usually taken to Sierra Leone, where they were released. British naval crews were permitted to divide prize money from the sale of captured slave ships. Apprehended slave runners were tried by naval courts and were liable to capital punishment if found guilty.