Perhaps "Extraterritorial regulation" is bad wording. A country can regulate whether an extraterritorial website is distributed and or viewed within its borders but it has no legal authority force another country to close down a website that's operating legally within its jurisdiction.
The only remaining options are diplomatic action—request the site be taken down or war/by force. Whether we like it or not the only practical action is for a country to geoblock offensive websites at its borders.
Sadly, given the current state of world affairs, it seems to me geoblocking will become the norm almost everywhere.