Top law enforcement officials in the United States, United Kingdom, and Australia told Facebook today that they want backdoor access to all encrypted messages sent on all its platforms. In an open letter, these governments called on Mark Zuckerberg to stop Facebook’s plan to introduce end-to-end encryption on all of the company’s messaging products and instead promise that it will “enable law enforcement to obtain lawful access to content in a readable and usable format.”

This is a staggering attempt to undermine the security and privacy of communications tools used by billions of people. Facebook should not comply. The letter comes in concert with the signing of a new agreement between the US and UK to provide access to allow law enforcement in one jurisdiction to more easily obtain electronic data stored in the other jurisdiction. But the letter to Facebook goes much further: law enforcement and national security agencies in these three countries are asking for nothing less than access to every conversation that crosses every digital device.

The letter focuses on the challenges of investigating the most serious crimes committed using digital tools, including child exploitation, but it ignores the severe risks that introducing encryption backdoors would create. Many people—including journalists, human rights activists, and those at risk of abuse by intimate partners—use encryption to stay safe in the physical world as well as the online one. And encryption is central to preventing criminals and even corporations from spying on our private conversations, and to ensure that the communications infrastructure we rely on is truly working as intended. What’s more, the backdoors into encrypted communications sought by these governments would be available not just to governments with a supposedly functional rule of law. Facebook and others would face immense pressure to also provide them to authoritarian regimes, who might seek to spy on dissidents in the name of combatting terrorism or civil unrest, for example.

The Department of Justice and its partners in the UK and Australia claim to support “strong encryption,” but the unfettered access to encrypted data described in this letter is incompatible with how encryption actually works.

Update 10/8: More than one hundred civil society groups, including EFF, have signed on to our own open letter to Facebook CEO Mark Zuckerberg, encouraging him to continue increasing security on Facebook messaging services.

“Given the remarkable reach of Facebook’s messaging services, ensuring default end-to-end security will provide a substantial boon to worldwide communications freedom, to public safety, and to democratic values, and we urge you to proceed with your plans to encrypt messaging through Facebook products and services,” the letter states.