Is there a way to disable a user to delete an attached file?

Is there a way to disable a user to delete an attached file?

Hi,

I've got a customer who processes a file that is uploaded by a user on a request. It happens that one user deleted the first file and uploads a second one with the same name but different content (as it is written in the request's history).
Is there a way to disable the removal of attachments by the user (beyond disabling "Requesters can edit" on "Advanced Portal Settings"?
With F&FR I only see mandatory capabilities on attachments.

Thanks.

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