consider it dropped -
but here's another passing thought on permissions. an epub is basically a zip, and zips can be locked + password protected. One of my shareware programs is sent to me like that for each update.
the pdf format also supports password locking, at 2 levels - you can lock just to prevent alterations ( that one is reasonably easy to remove) or you can lock to prevent unauthorised opening - & that requires a brute force crack AFAIK
does/could the epub spec support password protection ?
I realise that the current reader devices won't so it's not a full-on practical solution but in the future maybe ( & you could then block the kids from reading 50 shades of porn ! )