Spy on all citizens, foreign and domestic

The NYTimes report "Spying Program Snared U.S. Calls" claims that some domestic only phone calls were monitored "accidentally" -- yeah right.

What if the call was from US citizen in the US and US citizen in another country. Won't this violate the laws? Or what if it was an internet phone overseas? How can NSA tell who's what? Or does these accidental calls monitor just the "right" person(s)? I don't think so. And there are no oversight and punishments for breaking these laws.