Indeed, unless the traffic/file is explicitly labeled as encrypted (protocol, file header etc.) I think there's no way to tell if a particular piece of data is

Indeed, unless the traffic/file is explicitly labeled as encrypted (protocol, file header etc.) I think there's no way to tell if a particular piece of data is encrypted or not. More generally, the incredible stupidity in those calls for encryption bans is that the "bad guys" will abide to the law. There's a dark market for botnets etc., so why not for custom stealth encryption tools? I wouldn't be surprised if it already exists.