Actually, any US citizen working in concert with a foreign power is not longer protected.
Go read the law:
http://caselaw.lp.findlaw.com/casecode/uscodes/50/chapters/36/subchapters/i/toc.html
What if and this is a big the list of people that have been spyed on comes out and some of them are questionable (ie: political enemies etc....) what do the supporters of these actions say then?
I don't have a really big problem with the action of the POTUS, if and only if these actions were directly related to terrorists.