Imagine that you were designing this as a pen and paper game. No type systems, instances, or other computer language constructs. How would your "rule" system work then? How would you describe to a human player whether or not their character is allowed to use some weapon (or object in general)?
Choosing a specific example, let's say you tell them that swords can only be used by warriors. What questions might they have about this rule, and how would you answer them?