[Ed. – Have heard this from multiple sources in the last few days. It should concern Congress, and it appears the president is justified in fighting it (as his lawyers did by taking a complaint to Congress). This is something we should legitimately expect Rosenstein to address, rather than remaining silent on.]
As courts have held, emails between government employees remained privileged even though sent over government email servers. (In re County of Erie, 473 F.3d 413 (2d Cir. 2007). Courts held an ex-employee could assert attorney-client privilege against use of such emails by his company even though emails were located on employer’s computer and employer gave employee notice any documents stored on computer not protected. (Curto v. Medical World Communications (E.D. N.Y. 2006).
The Mueller search runs afoul of many of these established court precedents and Fourth Amendment privacy and privilege principles. First, it appears Mueller searched and seized every email, without any kind of categorical or keyword search. This is exactly the kind of search the Supreme Court made clear was not allowed under the Fourth Amendment. This means Mueller can only prevail if he didn’t seize a single email of a single individual that the individual could have any expectation of either personal privacy or attorney client privilege in.