Dissertation on Slavery by St. George Tucker
https://en.wikipedia.org/wiki/St._George_Tucker
http://www.gutenberg.org/ebooks/32239
The first introduction of Negroes into Virginia happened, as we have already mentioned, in the year 1620; from that period to the year 1662 there is no compilation of our laws, in print, now to be met with. In the revision made in that year, we find an act declaring that no Englishman, trader, or other, who shall bring in any Indians as servants and assign them over to any other, shall sell them for slaves, nor for any other time than English of like age should serve by act of assembly.