It had a visual touch of George Orwell's "1984." There on a large auditorium screen, Edward Snowden appeared from Moscow, as an enrapt audience of 500 sat in a University of Chicago auditorium.

But of course this wasn't Big Brother, the party leader and personification of constant surveillance. It was a cult figure of the opposite thrust, namely a self-styled whistleblower and free speech advocate. In a John le Carre construction, he might be called The Leaker Who Wouldn't Come in From the Cold.

The ultimately revealing encounter was the handiwork of the new and engaging Institute of Politics, founded by former longtime political strategist David Axelrod. It resulted from a fellowship stay at the institute by broadcast journalist Jessica Yellen, who in turn lured Snowden's Los Angeles-based ACLU attorney Ben Wizner to speak.

Axelrod raised the possibility of a Snowden appearance with the lawyer and then discussed it directly with Snowden via Skype. Last week, the former CIA contact sat in Moscow, where he's avoiding a U.S. trial on espionage charges, and was interrogated mostly by Geoffrey Stone, a longtime stalwart at the University of Chicago Law School.

It was both obvious and inspired. Stone is a prominent civil liberties expert and advocate who is a member of the National Advisory Council of the American Civil Liberties Union. But he's also now very much an expert in national security – certainly far more knowing than most Americans, including journalists who cover the area – precisely because of Snowden.

After Snowden's revelations and subsequent deep concern over government surveillance, President Obama appointed Stone a member of a special review group on Intelligence and Communications Technologies. The group was given essentially unfettered high-security access to our national security apparatus and ultimately made 46 recommendations on oversight of the National Security Agency, including how it collected telephone data on Americans and spies on international leaders.

The Institute of Politics' hour-long session with Snowden, which ended with student questions and applause, was not given to a debate between Stone and Snowden on any of many issues the former intelligence contractor touched upon. It left unclear what Stone really thought of Snowden, notably Snowden's justification for leaking documents and belief he served a higher purpose of popular understanding.

So I asked.

Before I ask about your response to Snowden during the session, describe any evolution of your thinking about the relevant issues during your tenure on the presidential panel.

Stone: So before I began the work on the review group, my general view was that, from what I learned in the media, the NSA had run amok and created these programs without appropriate approval or authorization or review. And whatever I thought of the merits of the programs, my assumption was that it was illegitimate because it didn't have appropriate review and approval. What surprised me the most was that this was completely wrong.

Every one of the programs the NSA was running in foreign intelligence surveillance was approved by the House and Senate intelligence committees, White House, the attorney general and the FISA (Foreign Intelligence Surveillance Act) Court. Every program was authorized and approved, and whatever one thinks of the programs, it was not a case of running amok or exceeding its authority. If there were extensive criticisms of the programs, the fault rests with the government entities that approved and authorized them. That I found surprising and illuminating.

The more I worked with the NSA, the more respect I had for them as far as staying within the bounds of what they were authorized to do. And they were careful and had a high degree of integrity. My superficial assumption of the NSA being a bad guy was completely wrong.

The second big change came as I understood these programs much better. I came to the view that they were well intentioned, that they were designed in fact to collect information for the purpose of ferreting out potential terrorist plots both in the U.S. and around the world and that was their design and purpose. And with a few errors of applications, it was the way in which they were utilized. By the NSA, there was no intentional abuse of the authorities they were given. And the purposes of the programs were good ones.

My concern I came to was, in a number of respects, that the programs could have been designed in ways that enabled them to be effective but better reduced the risks of impairing privacy and civil liberties. One example would be under the so-called Section 215 program, NSA was authorized to collect from phone companies the phone records of millions of Americans and keep them in an NSA database. NSA was then authorized to query that database – that is to essentially use a phone number belonging to a suspected terrorists to find out whom that suspected terrorist was in touch with, if it found reasonable grounds to do so. The risk is always there that some head of the NSA, or a J. Edgar Hoover or Nixon or LBJ would access those records for illegitimate reasons. So we required (in recommendations approved ultimately by Congress) that phone companies keep the data but not to give the mass of metadata itself to the NSA.

A second example: Under existing programs, NSA was authorized to query the database when NSA officials believed that a particular number was tied to someone engaged in terrorist activity. We urged that they had to go to the FISA Court to determine if reasonable grounds existed to believe that a number belonged to a person engaged in terrorist activities; a quasi-search warrant. It was an example of fine-tuning the programs to reduce risks to privacy and civil liberties. In our view the government and its entities are not looking hard enough for those opportunities.

At the heart of Snowden's appearance was his defense of his actions. How would you describe that defense and how do you respond? You didn't have a lot of time since it really wasn't a debate.

Stone: His basic defense is that "what I did accomplished much more good than it caused harm. And therefore what I did was justified." I would respond in several ways.

First, I think it is wrong. I think if he had only disclosed the existence of the second 215 metadata program, then one might be able to make the case he did more good than harm because there were reforms adopted because of his disclosures. That's a good thing. And the program itself had not been up to this point all that valuable, and therefore even though its disclosure makes it largely ineffective going forward – they work in part because the person you're surveilling doesn't know they exist – the cost was pretty modest because the program wasn't that valuable. On that one could make an argument that the benefit of the disclosure, which brought about reforms, was sufficiently beneficial so on balance a net good. If that was all he disclosed, you could make a reasonable argument for his proposition.

The problem is he disclosed vastly more than that, involving foreign intelligence not of Americans but of individuals who aren't American citizens in other countries. No changes were generally made in those programs and Americans don't really care. But disclosing those programs has had a serious impact on their being as effective as they had been. I think he did a lot more harm than good.

One example: One program lets the NSA gather email communications, including content of emails, not just phone numbers, targeting individuals who are not U.S. individuals, outside the U.S., where there's reason to believe the communications relate to terrorist activities. They can gather large amounts of email content, in so far as they have reasonable grounds to believe it's relevant to terrorist activity. Once disclosed, the terrorist knows this is going on and then takes measures to communicate in other ways. I don't have firsthand knowledge of this. My involvement ended before all the consequences could be evaluated. I have no doubt folks in the government are quite confident of that (the subsequent damage). It's quite logical.

Think of the metadata program. You are a would-be terrorist in Chicago and have no idea every call you make and receive is put in an NSA database. Everybody you speak with can be identified. You, like most people, use a phone to talk to friends and neighbors and people you are communicating with overseas about plots. So what do you then do? You buy a 'burner' phone, with no number registered to you, and completely circumvent the program. Really sophisticated terrorists probably did that already. But many were using phones that could be tracked through this program. I suspect that (use of traceable phones) has gone down dramatically.

The overseas, or 702, program brought lots of serious discoveries and let the NSA and other government agencies worldwide thwart terrorist attacks. The effectiveness of the program had to have been impaired. I know people in the government are quite concerned. And nothing changed. There were no reforms. No good has come of it (Snowden's disclosures), like section 215 programs. There's no positive impact.

What about Snowden's defense, or what he says about being unable to potentially mount the defense he thinks is fair? That's why he says he can't return to stand trial, given how the law under which he'd be prosecuted is written.

Stone: He wants a defense that doesn't exist: "You can violate law if you have good enough reason to do it." There is self-defense, allowing you to kill somebody when he is imminently going to kill you. But you can't rob people because you have hungry kids. It doesn't work that way. There is no general necessity defense that lets a jury balance costs and benefits when somebody violates a law.

At the end Snowden made a rather forceful defense of free speech, which in part seemed to prompt strong applause from the mostly student audience. What did you think?