Jonathan Adler wrote (and this sentiment has been widely written elsewhere):
A month later, the blog post is still there, and National Review is not backing down. Here’s the response from their lawyer, which notes (correctly in my view) that Mann is a public figure who would have to prove, by clear and convincing evidence, that NR published “a provably false statement” with actual knowledge the statement was false or “reckless disregard” for the truth or falsity of the statement. Further, the letter notes, in order to defend itself NR would be entitled to seek discovery, and in the process obtain access to e-mails and other records that Mann has, thus far, resisted disclosing in various freedom-of-information suits prompted by ClimateGate.(emphasis mine).
The "hockey stick papers," MBH98 and MBH99, were written when Mann was at the University of Massachusetts at Amherst, before he went to the University of Virginia. It's this work that Mark Steyn called "fraudulent," and while I'm no lawyer, I can't see how a court would allow a party to troll through any and all emails, especially those that came after the work that is the focus of the suit.
Do courts really allow those sued for defamation to have access to all of the plaintiff's correspondence and records -- all postal mail, all email, all voice mail, all documents, regardless of when they occur and their relevance? I seriously doubt it.