Colonial restrictions on the slave trade main took the form of slave import duties. Nine of the thirteen British North American colonies legislated in favour of such duties at one time or another before the War of Independence. Colonies passed such legislation to restrict slave imports when saltwater Africans were not required economically, when there were fears of slave revolts, in order to boost white immigration, manufacturing and trade and when military costs had to be met. South Carolina made particular use of high slave import duties to stop Africans being imported in the wake of the Stono rebellion of 1739, thereby supporting public safety against protesting slaves. The British parliament reserved the overall political and constitutional right to decide on the merits of slave trade restriction and its decisions were binding. The colonies did not combine to form an anti-slave trade stance before the meetings of the First Continental Congress in 1774, and even then the Guinea traffic formed just one element in the North American boycott of British goods in the tense couple of years leading up to the War of American Independence. Moral concerns about the slave trade were fairly muted in North America’s colonies before the War of Independence. The Quakers were at the forefront of anti-slave trade commentary but even they took decades to persuade their own membership to relinquish slave importation and slaveholding. New England clergymen joined by the 1770s in their condemnation of the slave trade. But there was no consensus in the North American colonies that consistent pressure should be exerted to proscribe the transatlantic slave trade. The trade was banned by most colonies in the non-importation protests of 1776–8, 1769–70 and 1774–6, but there were no detailed discussions about the subject at the two Continental Congresses after the Coercive Acts had been implemented in 1774.