A court order forcing former NSA contractor Edward Snowden’s email provider to turn over its master encryption key undermines a critical security feature used by major Internet services, the Electronic Frontier Foundation said Thursday.

The EFF, a digital rights watchdog, filed a brief on Thursday in support of the email provider, Lavabit, in the U.S. Court of Appeals for the Fourth Circuit.

Lavabit founder Ladar Levison was found in contempt of court for resisting an order to turn over his company’s private SSL (Secure Sockets Layer) key, used to encrypt communications for 400,000 users. He is appealing.

The U.S. government is believed to have sought access to the account of Snowden, who gave out a Lavabit email address after arriving in Russia, but he has not been named in the court documents.

Turning over the private SSL key would have allowed the government to potentially access the communications of all of Lavabit’s users, violating the U.S. Constitution’s Fourth Amendment protections against overly broad warrants.

“This is like trying to hit a nail with a wrecking ball,” the EFF wrote in its brief.

Service providers including Facebook, Google, Bank of America and Amazon rely on SSL—designated by “https” in a browser’s address field—to protect communications with users.

“Facebook has a single private key that protects the communications of over 1.26 billion users,” the EFF wrote. “In the case of Facebook, having the private key used by the company would give unfettered access to the personal information of almost 20 percent of all of the human beings on the planet obtained through the Facebook site for three years.”

The EFF argued that the breach of private keys could have a profound effect on the U.S. economy, with service providers likely to move to legal jurisdictions “that afford more protections for privacy and security.”

Lavabit was initially served with a pen register order that required it to provide metadata association with the email account the government sought. But like other privacy-focused email and VPN service providers, Lavabit’s systems were designed to not retain that information.

The company was then served with a warrant to turn over its private SSL key. Levison opted in early August to shut down Lavabit’s service, saying he could no longer guarantee the privacy of users.