Retaliate for... what? The whole point of "countries" is that other countries don't get to tell them how to run their country, unless there is a legally binding consortium agreement. If SK wants to make it hard or impossible for foreign countries to compete, that's literally up to them. It's their country. They make the rules.

If other countries give market access to Korean companies, then as a member of the WTO, South Korea's non-reciprocity comes with significant penalties.

This isn't about nimble startups being protected against Google and Apple. It's Naver, Samsung and Kakao Corporations. They sometimes exercise vast power over government and so such decisions are less democratic than oligarchic.

Let's remember that all this protectionism ends up costing consumers. UX design in Korean apps alone sucks so hard, and there's monopolistic pricing for lots of services. Consumers could benefit from alternatives.

And other countries make their own rules, which can include retaliation.