It depends on why the account was deregistered, really, somtimes it's temporary (like for the non-payment of fees, in that case once they're paid the account will usually be reinstated), and if the user closed their account, there's a limited timeframe in which they can cancel the request and keep the account open (I'm not sure when the account shows as NARU if the member requests to close it, but it's probably not until that timeframe is up, which would mean having to open a new account in that case).
