How do foreign regulators have jurisdiction over Disney/Fox merger?

Disney’s Fox deal approved by Chinese regulators as reported by the NY Post.

Why do Europe and China have jurisdiction over the merger of two US companies?

Because the companies operate in markets where there are regulations against monopolistic/cartelised behaviour and/or there are broadcasting licences at stake?

Most countries like to cling to the idea that they have some jurisdiction over what happens in their country.

Most big companies like to be sure they are going to be operating legally in whatever country.

Wouldn’t it depend on the presence of subsidiaries / significant business interests in those countries, sort of along the lines of how states only charge sales tax if there’s a significant company presence within that state?

They don’t have jurisdiction over the merger between two American corporations.

What they have jurisdiction over is whether a corporation can operate in their countries. As an example, the Chinese government can tell a corporation it can’t do business in China if it goes through with a merger it doesn’t like. The corporation will then consider the value of its business in China against the value of the merger and decide what’s in its best interests.

That is not how such scenarios are conceptualised in international antitrust law. The EU’s approach is to follow the effects doctrine: A merger between two foreign companies has to comply with EU antitrust law (or, as it is called in European legal terminology, competition law) if it has effects on the European market. That logic is not entirely uncontroversial under international law, but it is widely accepted as a potential basis for extraterritorial jurisdiction.

Of course, the way to enforce such laws is to threaten foreign companies “If you disobey our antitrust law we’ll fine you, and if you don’t pay these fines we’ll shut you out from our markets.”. But European antitrust law does claim for itself to have jurisdiction over the foregn merger itself, not just market access of the foreign companies in Europe.