This is not may area of expertise. I think someone with a background
in HR and Federal would probably be in a better position to answer.
Maybe even a company's Security Officer. You might try
https://workplace.stackexchange.com/ .
NIST sells the test cards to the general public. If there were
restrictions, then NIST would enforce it at the point of sale.
Foreign nationals cannot obtain a security clearance. If the project
has security requirements - and the employee is not cleared - then
they probably should not be working on the project. Confer,
https://www.clearancejobs.com/security-clearance-faqs.
I think what you will find in practice is, NIST usually covers US
Federal agencies like Social Security Administration and there are no
security requirements or simply a Public Trust. Companies doing
business with US DoD have security requirements and require employees
with clearances.
Jeff