ITAR is the US regulation controlling the export of defence articles and technical data. It reaches the front desk because letting a foreign national see controlled technology, even on a site tour, can count as an export. Facilities handling ITAR-controlled work therefore screen visitors for citizenship status before granting access.
Operationally that means visitor screening questions at pre-registration, escort rules for non-cleared guests, and a reliable log of who entered which areas. A visitor management system with screening workflows turns the compliance requirement into a standard sign-in step.