You can say this for the Senate intelligence committee's surveillance bill
: it goes to some length to guard against "reverse targeting" -- that is, tapping foreigners' communications into the U.S. when the real intention is to target a U.S. person, thus circumventing warrant requirements. The bill repeatedly bans the "intentional" targeting of U.S. citizens' communications without warrants.
For instance, the bill says
the NSA "may not intentionally target any person known at the time of the acquisition to be located in the United States," nor can it "intentionally" target a such a person "if the purpose of such acquisition is to target for surveillance a particular, known person reasonably believed to be inside the United States."
Should the surveillance happen
to target such a person, though, the collection can probably stand, unless the FISA Court finds -- after the fact -- that the procedures resulting in such accidental surveillance were unreasonable. However, as anyone who's ever watched a sporting event knows, lots of reasonable plans result in the opposite outcome from the one intended. And that doesn't mean the game stops.