The "Load and unload device drivers" user right must only be assigned to the Administrators group.
Inappropriate granting of user rights can provide system, administrative, and other high-level capabilities.
The "Load and unload device drivers" user right allows device drivers to dynamically be loaded on a system by a user. This could potentially be used to install malicious code by an attacker.
How this relates to the STIG checklist: STIG vs SCAP benchmark.