User blog comment:Callofduty4/Modern Warfare 3 Hardened Edition confirmed/@comment-1187034-20110725162241/@comment-356904-20110725181217

Correct. RIF is a very broad category, and includes Airsoft guns, deactivated weapons and non-firing dummies. The (more-or-less) exact wording is "anything that would be indistinguishable from an actual firearm".

To be sold legally to anyone without said defence, it has to be an "imitation firearm", which basically means 50% or more of the outer surface must be clear or painted a bright and unrealistic colour. Even then, the purchaser must still be over 18.