Can your refresh my memory, of such illegal spying? Also the GIANT difference is that US can legally spy on non US citizens, so even if I would complain that NSA hacked my company and stole a lot of people private data the Americans will just say "they did their job, all is legal" , there is need for an agreement so we respect each other citizens. if you think X is a terrorist and want to read his emails then does not matter if X is or not a US citizens you follow the laws and present a judge your evidence and ask for permission to spy.