A governance document written today can only govern what its authors thought to anticipate today. An AI agent that retrieves information at the moment it acts, a search, a database lookup, a document pulled into context, can encounter material the document never accounted for, because that material did not exist yet, or nobody thought to ask about it, when the document was written.
Security engineers have a name for a version of this problem: time-of-check to time-of-use, the gap between when a permission is verified and when it is actually exercised, during which the world can change underneath it. The parallel is not exact, TOCTOU is about access control evaluated at the wrong moment, and this is about a governance document's authority over content it could never have anticipated. But the shape of the gap is the same: something was fixed in advance, something else moved at runtime, and the fixed thing has no way to know.
This is not a drafting failure. No amount of additional care at authorship time closes this gap, because the gap is structural: retrieval happens after the document is written, by definition. You cannot pre-specify a response to content that does not exist yet. What you can do is stop treating the document as a wall that blocks everything outside its scope, and start treating it as a snapshot, current as of the moment it was written, that needs a mechanism for flagging when what it governs has moved past what it anticipated.
The practical question this leaves is not "how do we write a more thorough policy." It is "how do we know when the policy has met something it was never written for." I doubt your governance documents can answer that question today.