Ian F. Haney López, White By Law: The Legal Construction of Race (New York: New York University Press, 1996), 80-81.
Becoming White, then, is not an either/or proposition, but rather it is an uneven process, resulting in racial identities that change across contexts and time. Thus, in the 1920s eastern and southern Europeans could be White for purposes of naturalization, but still racial inferiors in the close context of immigration and the more general milieu of social relations. […] Recall now the question that opened this book. Judge  Smith in Shahid asked: “Then, what is white?” The above discussion suggests some answers. Whiteness is a social construct, a legal artifact, a function of white people believe, a mutable category tied to particular historical moments. Other answers are also possible. “White” is an idea, an evolving social group, an unstable identity subject to expansion and contraction, a trope for welcome immigrant groups, a mechanism for excluding those of unfamiliar origin, an artifice of social prejudice. Indeed, Whiteness can be one, all, or any combination of these, depending on the local setting in which it is deployed. On the other hand, in light of the prerequisite cases, some answers are no longer acceptable. “White” is not a biologically defined group, a neutral designation of difference, an objective description of immutable traits, a scientifically defensible division of humankind, an accident of nature unmolded by the hands of people. In the end, the prerequisite cases leave us with this: “white” is common knowledge. “White” is what we believe it is.