Yeah that's the tricky part. I don't think the EU could make Microsoft open source their Windows, but I guess something along the lines of Microsoft having to g

Yeah that's the tricky part. I don't think the EU could make Microsoft open source their Windows, but I guess something along the lines of Microsoft having to give access to their source code to a team of EU security researchers that audits and looks for backdoors would be a start. But even that isn't foolproof.