Lawyers of Lavabit, a secured email provider, has just filed a reply in brief to the Feds in a case that will determine how to handle over the master encyption keys for its entire system, in order to facilitate a court-approved surveillance of a single user in question.

Earlier this month, the government has defended its position to use a search warrant to obtain Lavabit's keys. In a brief at the 4th U.S Circuit Court of Appeals, the government has stated out that it needed the master keys to facilitate a "pen register" order allowing the FBI to collect email metadate - like "from" and "to" lines - on a particular unnamed target, believed to be NSA leaker Edward Snowden.

Lavabit founder Lader Levison, had offered to collect the email metadate himself and transmit it to the government after 60 days. But the government was insistent that he turn over the SSL key for the site right away, promising it would only use the key to monitor the targeted user and not Lavabit's 400,000 other users. They lost a court argument last August when they challenged it. Levison then stalled for two days, turned over the keys, and shut down his business on Aug 8, stopping any attempt at prospective surveillance.