:If you read the rest of the article, it says "Queen Isabella of Spain decreed that Spanish colonists could only legally enslave natives who were cannibals, giving the colonists an economic interest in making such allegations," citing as a source "Brief history of cannibal controversies" by David F. Salisbury, of Vanderbuilt University.  The introduction is a summary of the article, and finer points are covered elsewhere (or else we would not have the rest of the article).