Justice Anthony Kennedy-- who could proved the deciding "swing vote"-- went further with his skepticism.
"You are saying that the government has obtained this extraordinarily wide-reaching power and we have extraordinary risks that face this country and the government's not going to use it. It's hard for me to think that the government isn't using all of the powers at its command under the law -- in order to protect this country. And you want to say: 'Oh, well, don't worry that it's not happening. There is another statute.' That's the problem I have with this line of argument."
On the other side, Justice Samuel Alito appeared to agree with the government's contention that it cannot be proved the NSA conduct here had either occurred or was "certainly impending"-- the traditional legal benchmark to press a standing claim.
"If we accepted your other argument, that the plaintiffs have standing because they took preventative measures, wouldn't that undermine completely the 'certainly impending' standard," Alito asked ACLU lawyer Jameel Jaffer.
"You have a person who is in a situation where there is a certain risk of the person's conversation being intercepted, but it's not 'certainly impending.' So then the person simply takes some preventative measures," Alito said.
A coalition of legal, media, and human rights groups filed suit, many claiming that had been personally and secretly monitored. They worry such electronic dragnets could easily and unknowingly intrude on the privacy rights of all U.S. citizens. The government calls that "speculation" but cites national security in refusing to provide specifics.
The justices focused mainly on the "standing" question, and whether the ACLU lawsuit should move ahead. The broader constitutional privacy questions may not be addressed for perhaps another couple of years.
The case is Clapper v. Amnesty International USA (11-1025). A ruling is expected by spring 2013.