I do not agree with this ruling at all, but I do believe the defining point is that this ruling is that it pertains to the FBI only. Their jurisdiction is strictly US-oriented & any investigations they have outside of borders of the United States are restricted to United States citizens only. In short, if the FBI is hacking any system outside of the U.S., it's because they are investigating a crime involving a U.S. citizen as a participant.
Having said that, hopefully this will be shot down & over-turned as this really seems like the same rules/restrictions of wiretapping should apply (warrants issued, justified probable cause, etc.).
I was just telling a friend yesterday that one of the biggest problems we face in the world today is that we have a group of people crafting laws, rules, and regulations about objects and technology that they do not adequately understand to make such decisions in an informed manner.