Orin Kerr analyzes the filing by Lavabit:
Today Lavabit filed a brief before the Fourth Circuit challenging a civil contempt order for its refusal to turn over its encryption key that the government wants to enable the government to conduct surveillance of Edward Snowden. I think Lavabit faces a very uphill battle, and in this post I’ll explain why.
First, a bit of context. The government obtained several different court orders requiring Lavabit to disclose the key. First, they obtained a pen register order; next, they issued a subpoena for the key; and third, they obtained a search warrant for the key. Lavabit refused to comply with any of them, and the court imposed a fine of $5,000 a day until Lavabit agreed to hand over the key in digital form. (In a bit of a middle finger to the government and the court, Lavabit did turn over a paper copy of the key — which was 11 pages long in 4-point type — but refused to turn over an electronic copy. Understandably, the court didn’t consider that compliance.) Lavabit then shut down its service and handed over the key. In this appeal, Lavabit is appealing the lawfulness of the judge’s orders requiring it to hand over its key by arguing that none of the court orders were valid.
In order to to win on appeal, Lavabit needs to show that all three methods are improper. I don’t think they can do this. I’ll take each argument in turn.
Read his analysis on The Volokh Conspiracy.