Earlier quoted context omitted.
There is nothing that would stop this legally (what authority should hinder them?). Things that can be enforced are only limited by practicality. Any non-EU business worth enforcing such a law against will very likely do business inside the EU (e.g. selling ads to local companies). Any money transferred can then be froozen to enforce this law. Facebook in particular does business as an Irish company for its EU users,…
So, if you sell products or services in China, you have to comply to all China regulations, not just exports? That doesn't make any sense.
Respecting local regulations is not a mind blowing fact. A foreign company cannot sell heroin in the USA under the pretext it is legal in their country.