A senior adviser to the European Union's Court of Justice said Facebook and other social media platforms can be ordered to remove content that is equivalent to content that an EU court has deemed illegal, such as hate speech and defamation—a move that intensifies the debate on how far social media companies must go to monitor and control online content, even across borders.

The recommendation, if followed by the EU's Court of Justice, will increase the requirements on Facebook and other digital platforms to remove illegal content worldwide, although it does not require the company to carry out general monitoring for unlawful material.

Facebook was highly critical of the decision, saying it could have major implications for how it operates and undermine freedom of expression.

The Court of Justice follows the recommendations of its advocates-general in over 70% of cases.

The case involves Eva Glawischnig-Piesczek, an Austrian politician from the Green party, who sued in the Austrian courts, demanding that Facebook take down defamatory content that had been posted about her. Facebook blocked access to the content in Austria but the politician wanted the content removed so it could not be seen by other Facebook users outside her home country. She won in the lower court in 2017 and Austria's Supreme Court upheld the ruling on appeal but asked the ECJ to rule on whether it could be extended to apply to other postings with similar content worldwide.

The advocate-general, Maciej Szpunar, said that the EU's e-commerce directive provides that platform operators can be expected to remove defamatory content once they have been informed that the content is unlawful. They should not be required to carry out general monitoring for illegal content, the advocate-general found.

He also said that the approach represented a fair balance between the rights to protection of private life, the protection of freedom to conduct a business, and the protection of freedom of expression and information. It does not require sophisticated techniques that might represent an extraordinary burden for the company, he said.

At the same time, given the ease with which unlawful content can be copied and distributed on the internet, it was reasonable for the platform to make efforts to take down duplicate content that has been deemed illegal.

Facebook said in an emailed statement to Reuters that the case raises important questions about freedom of expression online.

“We remove content that breaks the law and our priority is always to keep people on Facebook safe,” Facebook said. “However, this opinion undermines the long-standing principle that one country should not have the right to limit free expression in other countries.”

The ECJ is expected to rule in the coming months.