When Alexa Koenig learned of Facebook’s abrupt decision to turn off a set of advanced search features last week, she thought of a Libyan military commander named Mahmoud Mustafa Busayf al-Werfalli.

In August 2017, the International Criminal Court issued a warrant for Werfalli for allegedly participating in or ordering the execution of 33 people in Benghazi, Libya. At the core of the evidence against him are seven videos, some of which were found on Facebook, that allegedly show Werfalli committing crimes. His case marked the first time the ICC issued a warrant based largely on material gathered from social media.

Now that kind of work is being put in jeopardy, according to Koenig, executive director of the Human Rights Center at the University of California, Berkeley. She said Facebook’s recent decision to turn off the features in its graph search product could be a “disaster” for human rights research.

“To make it even more difficult for human rights actors and war crimes investigators to search that site—right as they’re realizing the utility of the rich trove of information being shared online for documenting abuses—is a potential disaster for the human rights and war crimes community,” she said. “We need Facebook to be working with us and making access to such information easier, not more difficult.”

Simply put, Facebook graph search is a way to receive an answer to a specific query on Facebook, such as “people in Nebraska who like Metallica.” Using graph search, it’s possible to find public — and only public — content that’s not easily accessed via keyword searches.

Late last week, Facebook turned off several features that have long been accessible via graph search, such as the ability to find public videos that a specific Facebook user was tagged in. This set off a wave of concern among human rights researchers, journalists, law enforcement, and other advanced users. In tweets and comments to BuzzFeed News, they said the decision, which was not announced publicly, shows how Facebook’s response to data scandals and its resulting push to emphasize privacy is making it more difficult to investigate what happens on the platform.

Last year, for example, as it was facing criticism in the wake of the Cambridge Analytica revelations, Facebook turned off features that investigators use to find people on the platform.

A Facebook spokesperson emailed BuzzFeed News a statement that said the company has “paused“ some graph search features.

“The vast majority of people on Facebook search using keywords, a factor which led us to pause some aspects of graph search and focus more on improving keyword search. We are working closely with researchers to make sure they have the tools they need to use our platform."