This article investigates one of the neglected topics of slavery, namely the role of slaves, owners, overseers and certain officials in creating customary slave norms. The article focuses upon three to four interrelated customs concerning the slave's use of his free time, his right to work for himself on the Sabbath, his right to cultivate provision grounds and gardens for his own use and sustenance, and his right to keep the fruits of his own industry. These customs are traced from origins in the Caribbean under the Code Noir to further development in Louisiana and other slave societies.Four general points emerge about the customs of slavery. The first is that a dialectical relationship existed between the customs and the governing statutes and laws. The second is that the customs are an essential corrective to the impressions gained by reading those statutes in isolation. The third is that these customs, from a comparative point of view, played a similar role in the American South and in the British and French colonies in the Caribbean. The final point is to advance a theory of the origins of the customs. Building upon the comparative evidence and the theories of Lon Fuller and Bruce Benson concerning the origins of moral duties, I suggest that the customs are a form of compromise and negotiated behavior in a "war without arms." They arose from the need to introduce incentives into a system of involuntary labor. In this war of collective wills, slave resistance and legal consciousness were important creative elements in the development of the customs.