I've been following this case in the news.
My guess, and I am definitely not a legal expert, is this will be treated the same way as snail (hardcopy) mail. I have always been told that email is protected the same way as a letter sent in the mail is.
The big difference is method of access and spousal rights or lack thereof in this domain.
A roadside mailbox is protected from unauthorized retrieval of letters by persons not residing at the address, so electronic mail may be ruled to be of the same order under privacy laws.
We shall see what we shall see...