[unionpivo]

Well if the two US companies that do business in US and with US residents, than UK court would not have any jurisdiction. (And would not even try, it's not like they don't have other things to do.)

But in this case, you have two US businesses, that own local UK business and do business on UK soil with UK customers. That is why they fall also under jurisdiction of UK.

MS and Activison could close their business in UK, and stop serving their customers and then they would not be affected by UK courts.

Bottom line is, if you do business in multiple places, you need to play by the rules of all that places.

It's similar how the legislation in lets say California can affect products in all the USA.