Microsoft have to choose whether to operate in the EU. There's been a long struggle between conflicting rules of US unaccountable intelligence access vs. EU privacy law ("safe harbour") that is relevant here. https://blogs.microsoft.com/on-the-issues/2015/10/06/a-messa...
The combined armies of every member state of the EU, if it came to that.
Well before that point, they can just go through a normal court process because the EU has been empowered by the governments of each member state to write such legislation.
