Two companies who must remain anonymous about their fight against secret government demands for information known as national security letters (NSLs) are backing Twitter’s lawsuit over its rights to publish information about NSLs it may have received.  The companies—a telecom and an Internet company—are represented by EFF.

Twitter filed its suit in October, saying users deserved to know certain basic facts about NSLs that the government did or did not serve on the social media company.  NSLs—issued by the federal government but not approved by a judge—almost always contain a gag order barring the companies from notifying their customers or the public that any demands have been made.

The companies represented by EFF also want to go public with some details of their fights against NSLs, including their corporate identities and what they have done to protect their customers from unreasonable collection of information.  In an amicus brief filed today, they argue that the gag orders are an unconstitutional prior restraint on free speech and a serious infringement of their First Amendment rights.  However, the government continues to maintain that even identifying EFF’s clients as having received an NSL might endanger national security.