The decision comes in response to a controversial upcoming May 15 terms of service update that gives Facebook more data access than ever. This update would allow WhatsApp users’ details — including phone numbers and transaction information — to be available across other Facebook operations for the first time, in a reversal of WhatsApp’s previous policy.

Germany’s Regulatory Response

The regulator, the Hamburg Commissioner for Data Protection and Freedom of Information, opened emergency proceedings against Facebook last month. Now it has issued an injunction, a three-month emergency order to prevent Facebook from “further processing of WhatsApp user data,” says the head of the regulator, Johannes Caspar. Facebook has already responded, saying the regulation is “based on a fundamental misunderstanding” of the data processing update. So what exactly has caused such a big uproar? Here’s what data Facebook plans to process, and how it’s working to get all WhatsApp users to agree.

How the Update Rollout Works

Under the new terms, data shared across Facebook might include phone numbers, mobile device information, transaction data, IP addresses, and more, Engadget reports. Last year’s privacy policy for the messaging service let users opt to not share their account info with Facebook, making this new policy a direct about-face. WhatsApp’s May 15 update requires users to opt in, technically speaking. But the downsides to not opting to have Facebook access large amounts of your user data become gradually more extreme until the WhatsApp service is essentially unusable. Here’s how WhatsApp describes it on their site: This is true because the loss of functionality will come after May 15th. The same page goes on to explain that “after a period of several weeks,” the reminder of a need to update will become “persistent,” at which time users will indeed see a loss of functionality: In other words, WhatsApp users who don’t comply will eventually lose the ability to send and receive messages or calls via the service.   After a few weeks of limited functionality, you won’t be able to receive incoming calls or notifications and WhatsApp will stop sending messages and calls to your phone.”

Will the US Follow Suit?

Germany is the first to speak up about data-collection overreach in this particular case, but Facebook’s history of being challenged for vacuuming up more data than it should is a long and murky one. Some tech experts are arguing that state and federal agencies in the US should follow Germany’s lead, and move to stop Facebook from protecting its surveillance economics. A Time article from last month has even argued that the US needs a new agency to regulate operations like Facebook. Given the recent developments both in WhatsApp policy and in Germany’s regulatory action against the same, it’s hard to argue that the US shouldn’t take a harder look at Facebook’s stance towards its users’ data.