"was reduced from his former condition of servitude for a limited time to a condition of slavery for life." In 1670, the colonial assembly passed a law prohibiting free and baptized negroes and Indians from purchasing Christians, meaning whites, but allowing them to buy people "of their owne nation." In this meaning, "purchase" also related to buying the contract services of indentured servants of various "nations." In 1665 Anthony Johnson and his wife, Mary; his son John; and his wife, Susanna; and their slave, John Casor, moved to Somerset County, Maryland. Casor remained Johnson's slave for the rest of his life. Legal restrictions continued to be made related to African servants. The courts reasoned that "Insofar as Negroes were heathens, they could never become Englishmen; insofar as they were not Englishmen, they could not be entitled to the protections of the common law," which was limited to English subjects. Africans were considered foreigners or aliens. In 1662, the colony passed a law that children of enslaved women (who were of African descent and thus foreigners) were to take the status of the mother, rather than of the father, as was current under English common law. The principle, called partus sequitur ventrum, had been adopted from Roman law and caused children born of a free white mother and Negro father to be born free. In 1691, the law was amended; such mixed-race children had to serve as indentured servants for 30 years while the mother would be fined fifteen pounds sterling. If the mother failed to pay the fine within a month of birth, she was indentured herself for five years. By the end of the 17th century, colonists were importing many Africans via European slave traders as slaves to satisfy the demand for labor. There was limited demand for slaves and trade with America was not profitable, with the trade with the West Indies and South America remaining far more lucrative. The most likely source of slaves was directly from the West Indies, rather than Africa, through the contacts that the American colonists maintained with the European colonies in the region. By an act of 1699, the colony ordered all free blacks deported, virtually defining as slaves all people of African descent who remained in the colony. Most historians argue that John Punch, an African who was ordered indentured for life in 1640, should be considered the first documented slave