When multiple employees enter a building using one person's ID badge (tailgating), which security control is violated?

Tailgating directly violates physical access control because it bypasses established security measures designed to restrict entry to authorized individuals. Physical access controls, such as ID badge readers and turnstiles, are implemented to ensure only those with proper credentials can enter a secure area. When someone "tailgates," they circumvent these controls, gaining unauthorized physical entry. While user awareness (of security policies) is important to prevent tailgating, the violation itself is against the physical access control system. Intrusion detection systems monitor for unauthorized activity after entry, and network authorization deals with access to network resources, not physical entry.