Isn't the key this sentence: "Wired reported the government as complaining that a Lavabit representative indicated that Lavabit had the technical capability to decrypt the information, but that Lavabit did not want to ‘defeat [its] own system."?
If they used something like Perfect Forward Secrecy, could they not legitimately have claimed to be unable to defeat their own system (as it is currently configured)?
If they used something like Perfect Forward Secrecy, could they not legitimately have claimed to be unable to defeat their own system (as it is currently configured)?