Four major tech firms have agreed to remove hate speech from social media and similar services within 24 hours of it being reported. The move, which comes in a European code of conduct, will only apply to content which breaks the law.

That limitation means it could be a tricky subject deciding what material comes under the code, depending on the location of the person making the posts, the physical location of the servers hosting and delivering it, and the country in which the relevant service is legally registered.

The code of conduct involves Facebook, Microsoft, Twitter and YouTube, along with the European Commission. That’s the administrative wing of the European Union, a grouping of 28 countries.

The key point in the code is “the continued development of internal procedures and staff training to guarantee that they review the majority of valid notifications for removal of illegal hate speech in less than 24 hours and remove or disable access to such content, if necessary.”

All countries in the European Union agreed to a legal principle in 2008 to criminalize “the public incitement to violence or hatred directed against a group of persons or a member of such a group defined by reference to race, color, religion, descent or national or ethnic origin.” It was then up to each country to pass its own specific national law to implement this principle.

Under the code, the tech companies will need to take account of the appropriate national law when deciding whether to remove the content.