Your phone knows where you are, because it’s there with you. And when you use social media to post photos and talk with friends about an event you’re at, that’s data that can be scraped and used… including by cops who want to figure out what you’re up to. But not so fast, Facebook now says: If you want to build an app for surveillance, you’re going to have to do it without their data.

There have been instances of law enforcement using Facebook data to cast a wide net — not just look for information on specific suspects in specific investigations — before.

The ACLU published a report last October detailing how law enforcement agencies used a company called Geofeedia to help target protesters.

Geofeedia used Facebook, Instagram, and Twitter APIs — the things that developers can plug into, in order to use data from a platform — to create real-time maps of protest activity. Those maps were then used to identify, and sometimes arrest, protesters.

When the ACLU contacted the companies with its findings, all three social networks cut off Geofeedia’s access to their platforms. At the time, the Twitter terms of service for developers banned using user data specifically for surveillance; Facebook’s, meanwhile, had rules against putting user data into a search engine or directory without permission.

Facebook has now explicitly decided to make “surveillance” against the rules, though. Its updated developer policy now says that developers agree to “Protect the information you receive from us against unauthorized access, use, or disclosure,” adding, “For example, don’t use data obtained from us to provide tools that are used for surveillance.”

Facebook deputy chief privacy officer Rob Sherman also shared a post explaining the company’s reasoning on its U.S. Public Policy page.

“We are committed to building a community where people can feel safe making their voices heard,” Sherman wrote.

“Our goal is to make our policy explicit. Over the past several months we have taken enforcement action against developers who created and marketed tools meant for surveillance, in violation of our existing policies; we want to be sure everyone understands the underlying policy and how to comply,” he continued, before concluding with a shout-out to the ACLU and a plug for an SXSW panel where the ACLU would be discussing social media surveillance with experts.

The ACLU, for its part, applauded the change.

“We depend on social networks to connect and communicate about the most important issues in our lives and the core political and social issues in our country,” Nicole Ozer, Technology & Civil Liberties Director at the ACLU of California, said in a statement.

“Now more than ever, we expect companies to slam shut any surveillance side doors and make sure nobody can use their platforms to target people of color and activists.”

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