PGP encrypts the body of the email. It leaves the metadata as-is. There's a surprising amount of information in there - the subject, to/from, IP addresses, DKIM

PGP encrypts the body of the email. It leaves the metadata as-is. There's a surprising amount of information in there - the subject, to/from, IP addresses, DKIM signing information, References headers, etc. This would likely be enough information for a lot of the metadata path discovery that the government wants to do.