A pro-privacy email service long used by NSA leaker Edward Snowden abruptly shut down today, blaming a secret U.S. court battle it has been fighting for six weeks – one that it seems to be losing so far.

"I have been forced to make a difficult decision: to become complicit in crimes against the American people or walk away from nearly 10 years of hard work by shutting down Lavabit," owner Ladar Levison wrote in a statement. "After significant soul searching, I have decided to suspend operations."

Based in Texas, Lavabit attracted attention last month when NSA leaker Edward Snowden used an email account with the service to invite human rights workers and lawyers to a press conference in the Moscow airport where he was then confined. A PGP crypto key apparently registered by Snowden with a Lavabit address suggests he's favored the service since January 2010 – well before he became the most important whistleblower in a generation.

Levison posted this message today announcing the shutdown.

My Fellow Users, I have been forced to make a difficult decision: to become complicit in crimes against the American people or walk away from nearly ten years of hard work by shutting down Lavabit. After significant soul searching, I have decided to suspend operations. I wish that I could legally share with you the events that led to my decision. I cannot. I feel you deserve to know what’s going on–the first amendment is supposed to guarantee me the freedom to speak out in situations like this. Unfortunately, Congress has passed laws that say otherwise. As things currently stand, I cannot share my experiences over the last six weeks, even though I have twice made the appropriate requests. What’s going to happen now? We’ve already started preparing the paperwork needed to continue to fight for the Constitution in the Fourth Circuit Court of Appeals. A favorable decision would allow me resurrect Lavabit as an American company. This experience has taught me one very important lesson: without congressional action or a strong judicial precedent, I would _strongly_ recommend against anyone trusting their private data to a company with physical ties to the United States. Sincerely,

Ladar Levison

Owner and Operator, Lavabit LLC Defending the constitution is expensive! Help us by donating to the Lavabit Legal Defense Fund here.

Reading between the lines, it's reasonable to assume Levison has been fighting either a National Security Letter seeking customer information – which comes by default with a gag order – or a full-blown search or eavesdropping warrant.

Court records show that, in June, Lavabit complied with a routine search warrant targeting a child pornography suspect in a federal case in Maryland. That suggests that Levison isn't a privacy absolutist. Whatever compelled him to shut down now must have been exceptional.

A voicemail to Lavabit went unreturned today.

Update 19:45: Lavabit has 350,000 users who aren't Edward Snowden, and some are decidedly unhappy with Levison's decision, judging by a flood of angry comments posted to Lavabit's Facebook page this afternoon.

"Too bad that I payed some years in advance to keep up the good work that now turns out to be terminated without any warning," wrote one user. "I relied on this service which is basic for my private as professional online communication and have no idea how to migrate mails and recover mails being sent that never reached me in the past 18 hours."

"I have my Steam account and EVERYTHING on Lavabit," wrote another. "Please have the servers running so that we can migrate our services."

"How am I supposed to migrate?" a third user added. "Some services require a confirmation sent to the old email address to be able to switch. I can't believe this. I just switched to Lavabit only a couple of weeks ago to get away from Hotmail snooping my shit."

A minority of commenters were more supportive. "Holy shit, you guys are crying over your Steam accounts," wrote one. "Just change your email to something else. Lavabit either had to roll over for the government, compromising our privacy, or shut down service. Be happy Ladar shut it down instead of rolling over."