While massive tech rivals spend a lot of their time at each other's throats, there are occasions when they work together for a mutually beneficial cause. Samsung’s patent dispute last year is one example, as is the FBI iPhone saga, and now another case is uniting companies from within and outside of the tech industry: Microsoft’s battle with US government over the Electronic Communications Privacy Act (ECPA).

Amazon, Apple, Google, and Mozilla have all filed an amicus brief supporting Microsoft’s lawsuit, which aims stop the ECPA from allowing officials to determine when or if companies can notify customers of government information requests. Gagging orders, essentially.

Other firms lending their support include the U.S. Chamber of Commerce, the National Association of Manufacturers, Delta Air Lines Inc, Eli Lilly and Co, BP America, the Washington Post, Fox News, the American Civil Liberties Union, the National Newspaper Association, the Electronic Frontier Foundation, five former FBI and justice department officials, and many others.

The unlikely alliance prompted Microsoft’s chief legal officer, Brad Smith, to joke: "It’s not every day that Fox News and the ACLU are on the same side of an issue." He previously said in a blog post that consumers and businesses have a right to know when the government accesses their e-mails or records

The companies believe that not notifying customers of the requests is a violation of the fourth amendment, which establishes the right for people and businesses to know if the government searches or seizes their property. Microsoft claims it also violates its First Amendment right to free speech.

Despite all the support, there’s no guarantee that Microsoft’s lawsuit will be successful. The justice department has said there’s “compelling” interest in keeping criminal investigations secretive, and that there are steps to protect constitutional rights. It hasn’t commented on the recent friends-of-the-court filings.