I don’t think liberal democracies should ban travelling to other countries - even states like North Korea with odious, horrific tyrannies that make China seem like the land of freedom, milk and honey.
Britain just strongly advises going to certain places instead (and airlines and insurers take notice of Foreign Office Travel Advisories), though I’ve heard it’s illegal for Americans to visit Cuba and Iran (?).
Though I guess South Korea is still technically at war with North Korea, given the lack of a formal peace treaty following the Armistice, esp. given recent hostile acts by the North.
