Apple, Amazon, Cisco, and Microsoft are supporting Google in a new fight against the FBI.

The technology giants filed an amicus brief in Pennsylvania this week after a court ruled that Google must hand over emails in response to an FBI search warrant.

Apple knows all too well what it’s like to battle with the FBI. After a judge ruled last February that the company must unlock an iPhone used by a San Bernardino shooter, Apple refused and became embroiled in a legal battle with the bureau that went on for months.

Google, Facebook, and other Silicon Valley giants backed Apple’s decision not to create an iPhone backdoor that would compromise the security of iOS. Now Apple is returning the favor by standing alongside Google in its fight against an FBI search warrant.

“When a warrant seeks email content from a foreign data center, that invasion of privacy occurs outside the United States — in the place where the customers’ private communications are stored, and where they are accessed, and copied for the benefit of law enforcement, without the customer’s consent,” reads the brief filed by Apple, Amazon, Cisco, and Microsoft.

The companies argue that granting access to the FBI would “invite” other countries to demand emails sent and received by U.S. citizens, stored on U.S. soil, using the same methods. They also believe that it would be seen as an extraterritorial act.

“Our sister nations clearly view US warrants directing service providers to access, copy, and transmit to the United States data stored on servers located within their territory as an extraterritorial act on the part of the US government.”

It’s not completely clear what data Google has been asked to hand over to the FBI, but the company first confirmed last month that it would be fighting the request. It also stated that it would “continue to push back on over-broad warrants.”

Google’s argument hinges on the U.S. Stored Communications Act, and whether it applies to data stored abroad. According to the amicus brief, it should be up to Congress, not the courts, to decide that.