This policy key controls the behavior of how Office documents should be handled when they fail File Validation. The options ...

This policy key controls the behavior of how Office documents should be handled when they fail File Validation. The options available are, 

- Block files completely. This will prevent users from opening files.
- Open files in Protected View and disallow edit.  This will prevent users from editing the files.
- Open files in Protected View and allow edit. This will allow users to edit the files.

If you disable or do not configure this policy setting, the default setting will be, "Open files in Protected View and allow edit."