Elias Neibart has posted Indians and Citizenship: Territorial Birth & Parental Status in Contemporaneous Caselaw on the web. Here are two paragraphs from the introduction:
Originalist scholars have weighed in. On one side of the debate is Professor Ilan Wurman. He has argued that “birthright citizenship depended largely, even if not exclusively, on the status of the parents as being within the allegiance and under the protection of the sovereign.” If a parent was “within the allegiance and under the protection of the sovereign,” he was subject to the sovereign’s complete “municipal jurisdiction.” And, if that were the case, any children that parent had would be bona fide citizens of the polity. Others disagree with Wurman’s focus on parental status. Professor Keith Whittington, for example, has argued that, “except under very narrow exceptions,” “[c]hildren born within the territory of the United States are natural-born citizens.”The status of one’s parents, in this account, is largely immaterial. As long as you are “born within the governing authority of the nation,” you “are thereby subject to its jurisdiction.” For Whittington, citizenship hinges upon where you are born.
The status of Indians presents a conceptual problem for Whittington’s view. After all, those born to “parents in a Native American tribe” are “born within the geographic territory of the United States.” But it’s widely understood that those children are not citizens under the Fourteenth Amendment. Whittington deals with this issue by arguing that “[t]he critical point . . . was that Indians born on tribal lands were foreigners to the United States.” But, for him, “the land is doing the important work. Indian land is within the territory of the United States but is not governed by the United States.” To Whittington, “the Reconstruction Congress was . . . concerned with whether ‘Indian country’ was governed by American law.” Put another way, the central question was whether a child was born on “sovereign territory” (i.e., Indian land).