The European Union's highest court has ruled that member states can order Facebook - and other online services - to remove illegal content beyond their borders.

Platforms may also have to seek out similar examples of the illegal content and remove them, instead of waiting for each to be reported.

This case arose from a dispute in the Austrian national court between Facebook and a Green Party politician, who claimed that material about her published online was defamatory.

The court agreed, but wanted to know whether EU law allowed it to order the company to delete not just the offending item itself, but also identical or similar content stored elsewhere.

The European Court of Justice decided that there was nothing in EU legislation to prevent it from doing so.

Legal experts suggested the ruling had global implications for online platforms.

Facebook said it undermined the principle that one country did not have the right to impose its own laws on speech on another.