Some context for people who think that Anthropic can readily verify that someone isn’t a foreign person, since they already verify age (via persona, IIRC).
Immigration status isn’t in any commercial IDV dataset like Persona or LexisNexis, and an SSN won’t tell you either, since work-authorized visa holders have one too, and would fall under the ITAR definition of a foreign person. Immigration status databases run by the govt like E-Verify and SAVE are for employment and benefits, not export controls.
The only way I can think of is making users upload a passport, green card, or birth certificate, and then you get into document authenticity concerns. This is a much more complex verification requirement when compared to age.