Enabling "Prohibit Archiving" from Archive Policy settings does not restrict users from creating local archive for local mail file replica
Enable "Prohibit Archiving" field from Archive Settings -->Basics Tab--> Archiving Options section. Policy gets applied to server mail file copy & restrict users from creating archives from server copy however users still can create archives from local replica.
Before applying the policy, if the user is already having private archiving criteria and created the local archives then archive profile gets created in local mail file copy. If this archive profile is already present then policy is not effective for local mail file copy and users can still use private archiving criteria.
Resolving the problem
To resolve the problem, you need to delete "Archive" profile from local mail file replica.
You can create a hotspot button and use below script to delete the archive profile.
Just create a new message and then click anywhere in the body of message and then go to Create > Hotspot > Button and paste the following code in the "Click" event of the button. Always paste the code between "Sub Click" and "End Sub" keywords. You can send this message to user and ask user to click on button.
Dim session As New NotesSession
Dim db As NotesDatabase
Dim doc As NotesDocument
Set doc=db.GetProfileDocument("Archive Profile")
Msgbox "Profile Document is Successfully Removed"