Jus soli citizenship is based on the land of birth and jus sanguinis is citizenship based on parentage. In the oral arguments of Tuan Anh Nguyen v. INS (No. 99-2071), Justice Ginsburg made it clear that her view is that natural born citizenship can be conveyed by parentage alone and doesn’t necessarily require birth in the United States. She rejected the formulation of de Vattel, in The Law of Nations, that birth in the country of citizen parents is necessary for naturels.
Here is the relevant section from the transcript:
Justice Ginsburg: …My grandson was born in Paris of U.S. citizen parents. I had never considered him a naturalized citizen of the United States….
Justice Ginsburg: There is a debate over whether my grandson is a natural born citizen. I think he is.
Listening to the transcript points out how detached from reality are the denialist lawyers like Apuzzo and Donofrio, trying to rewrite American history and citizenship law.