The top European Union court said Thursday that Facebook and other platforms can be required to remove illegal content worldwide, a ruling with global implications that pits the social media giant’s free speech ethos against laws in other countries.

The E.U. Court of Justice ruled Facebook and other platforms will need to remove information or block access to any illegal material, including in some instances content that is “equivalent.” Judges can also order it taken down worldwide, “within the framework of the relevant international law.”

The decision upheld an Austrian ruling in which a politician sued Facebook to remove defamatory content and the court ordered it be removed globally. Facebook had previously removed the content in Austria only.

In an internal Facebook meeting that was streamed on Mark Zuckerberg’s Facebook page Thursday, the CEO called the ruling “a very troubling precedent to set.”

“This is going to be something that I imagine we and other services will be litigating and try to get to clarity about what this means over a long period of time,” he added.

The ruling has the potential to change the landscape for social media companies, which will be required to police content across their sites in direct contradiction to a preference toward free speech. It also upends previous tendencies toward country-by-country legal decisions on these types of issues.

“It’s troubling because once other countries go down this route, it’s going to be a free-for-all,” said Daniel Castro, vice president of the Information Technology and Innovation Foundation, a nonprofit think tank. “A particular royal could say, ‘No, you cannot insult the king or queen,’ and Facebook could have to enforce that globally, possibly even for speakers outside of the country.”

Facebook spokeswoman Sarah Pollack said in a statement that the ruling could have a chilling effect on free speech and “raises critical questions around freedom of expression and the role Internet companies should play in monitoring, interpreting and removing speech that might be illegal in any particular company.”

In the United States, a 1996 law known as Section 230 of the Communications Decency Act protects Internet companies from liability for content created by their users. The protections allowed social media companies to grow, protecting them from legal liability from everything from users’ product reviews to political rants. But it’s recently come under attack from Democrats and Republicans.

In response to some of those concerns, Facebook last month unveiled a blueprint for a roughly 40-person panel to form an independent oversight board. The group will act as the company’s version of a Supreme Court, dealing with appeals to the company’s moderation decisions regarding the posts, photos and videos it takes down or leaves online.

While Facebook is not allowed to appeal the ruling, Castro said individual European countries could choose to not to ask tech companies to remove content globally or countries like the United States could use trade agreements to pressure the E.U. for more expansive Internet freedom. The E.U. is reviewing its e-Commerce Directive and Digital Services Act, said Castro, so changes to those legal frameworks could also impact the effect of the ruling.

The decision comes about a week after the same court made a contrasting ruling in a case involving Google. In that case, the court determined the E.U.’s right-to-be-forgotten doctrine, which gives residents more control over sensitive information that appears online, does not apply to search results worldwide.

Though the U.S. Congress has in recent years increased its scrutiny of the tech industry’s data and privacy practices, Europe has taken the lead in investigating and regulating the sector. European regulators fined Google about $1.7 billion in March on charges that its advertising practices violated antitrust laws. U.K. watchdogs last year were the first to fine Facebook for a lack of privacy protections in the wake of Cambridge Analytica. E.U. regulators are also looking into whether Amazon is misusing data from third-party sellers to develop and market the company’s own products.

Google and Amazon did not immediately respond to a request for comment.

Thursday’s ruling stems from a 2016 case in which Austrian politician Eva Glawischnig-Piesczek sued Facebook Ireland for what she alleged to be defamatory comments alongside a news story shared on its platform.

According to court documents, a user accused Glawischnig-Piesczek of being a “lousy traitor of the people,” a “corrupt oaf” and a member of a “fascist party” after the Austrian Green Party member posted a news story titled “Greens: Minimum income for refugees should stay” that also generated a thumbnail image of the politician.