Evolution of ‘white’ from 1790s to 1890s – ‘sociohistorical boundary crossing’ of legal terms. / WBL 126-7.
In addition to legitimating race, legal rules operate as an idea-system to construct races in a second way. Though race as a social concept has some autonomy, it is always bounded in its meanings by the local setting. Laws help racial categories to transcend the sociohistorical contexts in which they develop. For example, the original prerequisite statute was written in 1790, when popular conceptions of race on the eastern seaboard of North America encompassed only Whites, Native Americans, and Blacks. As a legal restriction on naturalization, however, the “white person” prerequisite of 1790 was imposed on Bhagat Singh Thind on the West Coast of the United States in 1920. It is most unlikely that those who wrote the first prerequisite law intended either to include or to exclude South Asians, for that group almost certainly existed outside the realm of their world knowledge. […] Nevertheless, partially by its institutionalization in law, the category of ‘white persons’ transcended the local boundaries of time, place, and imagination in which it had one meaning, persisting and expanding into  remarkably different locales, where, though with a facade of continuity, it took on various new definitions.
This sociohistorical boundary crossing is normal to law.. One of the defining elements of law is its universal aspiration, its will to apply equally in all cases and across all situations. However, the pursuit of universality in law can make it a profoundly conservative force in racial construction. Here, the role of precedent is particularly important. Racial lines are prevented from shifting to the extent that past racial definitions control decisions about race in the present. “Reasoning by analogy to precedent cases creates a false historicity in that it perpetually reclaims the past for the present: in theory a dispute in 1989 can be resolved by reference to cases from 1889 or 1389.” Of course, the dead hand of the past does not completely control the present; precedent is often manipulated, and such manipulation is central to legal change. Nevertheless, by giving great weight to superannuated racial definitions, precedent keeps alive restrictive notions of race.
Consider the Mashphee Indian case. [… difficulty of proving they were a “tribe” according to Supreme Court standards from 1901…]  In this way the use of precedent in law provides a conserving, stabilizing force in racial construction by preserving the relevance of past racial definitions, thereby allowing such categories to transcend their local settings.
Law frees racial categories from their local settings in another, quite distinct sense, as well: it occasionally provides new language with which to construct racial differences. Legal terms that do not refer explicitly to race may nevertheless come to serve as racial synonyms, thus expanding in often unpredictable ways the form and range of racial categorization. This possibility is evident in the prerequisite cases, though it is much more relevant to the legal construction of race today. The prerequisite laws spawned a new vocabulary by which to mark racial difference, the phrase “alien ineligible to citizenship.” Congress and a number of states used this phrase to avoid the Fourteenth Amendment’s bar against invidious race-based discrimination. In 1922 Congress proscribed the marriage of U.S. citizen women to non-White aliens by providing that “any woman citizen who marries an alien ineligible to  citizenship shall cease to be a citizen of the United States. Two years later Congress relied on the same phrase to ban unwanted races from the country, mandating that “[n]o alien ineligible to citizenship shall be admitted to the United States” except under restrictive circumstances. [… use in alien land laws, struck down eventually in Oyama …] Legal language can allow ideas of race to transcend their historical context through precedent, and also can contribute to the construction of race by providing a new vocabulary with which to take note of, stigmatize, and penalize putative racial differences. Law thus frees racial categories not only from contextual bounds, but also from the bounds society places on the use of race. […] As will be emphasized later, the law’s ability to provide seemingly neutral synonyms for race may be one  of the most important legal mechanisms in current processes of racial construction.
Ian F. Haney López, White By Law: The Legal Construction of Race
(New York: New York University Press, 1996), 126-130.