Lavabit’s founder has filed the opening brief in his appeal against a court order forcing him to turn over the keys to his secure email service’s encryption.

Ladar Levison, who set up Lavabit in 2004, was commanded to turn over the encryption keys in electronic format by the district court for the eastern district of Virginia. When he refused, the court found him in contempt, and instituted a fine of $5,000 a day until he complied.

Levison handed over the data, but closed his business to protect his customers’ information. “The government would still be able to use Lavabit's private keys to decrypt and access data that it had already intercepted (including customers' usernames, passwords, and the contents of their emails),” the appeal details, “but Lavabit was forbidden from communicating this security breach to its customers or business partners.”

The appeal which followed rests on three arguments. “First, the government is bereft of any statutory authority to command the production of Lavabit's private keys … Second, the Fourth Amendment independently prohibited what the government did here … Finally, the grand jury subpoena was oppressive, unduly burdensome, and ought to have been quashed.”

Speaking before the appeal was filed, Levison said “I just think it’s important … to understand that even though this investigation was over one person, [the government was] doing two things: it was [not only] demanding information which belonged to the user, but [also information which] belonged to the business.

“It’s not like they were asking for a photocopy of my tax return: this was highly sensitive information which belonged to my business, and it was going to provide access to everyone and everything going over my network.

“From a security standard, that’s just game over. How can you protect a network if they’re able to see everything that comes over it?”

Although he is unable to specify who the targets of the investigation were, Levison said "I only know about a small number, but it was more than one. What the press is focusing on is one particular investigation. But they had more than one investigation simultaneously." Edward Snowden, the NSA leaker, used the Lavabit service, and is believed to be the principal focus of the investigation.

On Wednesday, Levison revealed that he had attempted to forestall the government’s request for his private keys by offering to log metadata himself.