The British Parliament is an institution that helped shape and construct the present international order, at one point holding jurisdiction over a quarter of th

The British Parliament is an institution that helped shape and construct the present international order, at one point holding jurisdiction over a quarter of the Earth's surface area. Yeah, this guy is a US citizen, but he is the officer in charge of a multinational corporation that does business in and draws revenue from the UK and its dependents. Is he legally obligated to show up? Probably not. Would Parliament be able to enforce their decision if they decided he was legally obliged? Probably not, not in the case where they come up against the US though if he were resident in nearly any other country in the world though, they probably could. International law relies on conventions agreed upon by nation-states, themselves a hodgepodge of various domestic and foreign interests. The only really big enforcement actor in the space is the United States Military, and so in cases where the United States Military isn't willing to take action for domestic reasons, international law basically means nothing. So while Zuckerberg may not have to go himself, he probably should or just cut business ties with anybody in the UK now. They may not be able to force him by military might, but they can make his life difficult and Facebook's continued operations in the UK very very difficult. Oh and do note that Facebook hosts British data globally, even if operations are conducted locally. In their position I would be going after the parent company, not the local stub unless I had to make a few examples out of the local stub to get the parent company's attention.