The southern colonies imported more slaves, initially from established English colonies in the West Indies. Like them, the mainland colonies rapidly increased restrictions that defined slavery as a racial caste associated with African ethnicity. In 1663 Virginia (followed by others) adopted the principle in slave law of partus sequitur ventrem: that children were born into the status of their mother, rather than taking the status of their father, as was then customary for English subjects under English common law. This meant that children of slave mothers were also slaves, regardless of their fathers and ethnicity. In some cases, this also could result in a person being legally white under Virginia law of the time, although born into slavery.