I tend not to see every presidential policy speech as legacy-defining, but Friday's speech might just fit the bill. Obama has used his second term to review and claw back the advancing national security state that he endorsed and expanded when he took office. I've written this before, but he really does not want to be known as the president who enshrined indefinite detention of terrorism suspects into law, or who abused the state secrets privilege, or who allowed the surveillance state to run amok. Geoffrey Stone, a law school colleague of Obama's who also served on his intelligence review panel, told me a long time ago that Obama, in his core, viewed himself as a champion of civil liberties and would be disappointed in himself if he did not leave a legacy of having advanced the ball down the field. To put it another way, Obama does care whether Americans perceive him to be a defender of their liberties.

Obama also cares about world opinion. In much the same way, although not to the degree, that George W. Bush did not want Muslims around the world to see themselves as the objects of his war on terrorism, Obama does not want the average person in the developing world to see himself as a legitimate target of American surveillance. If Obama changes the rules about targeting foreigners, he'll do so not because he believes that non-Americans deserve the same protections as Americans, but because he believes that it is not in America's interests for the average person around the world to be afraid of, or to have a reason to distrust, America and its actions.

Suffice it to say, Barack Obama is in a predicament. He does not possess the superhuman ability to serve, simultaneously, several compelling national interests:

- The need to preserve a functioning, adaptive, and powerful intelligence agency that provides the president with significant decision advantage;

- The need to placate Americans who believe that agency is out of control and who tend to believe the narrative presented by the agency's critics;

- The need to define, as best as possible, a concept of privacy that intuitively tracks with what most Americans believe it to be, and one that is inviolate enough, surrounded by a defense of laws and oversight, to allow the debate about NSA abuses to recede into the past.

What he won't even try to do is accept the terms of the debate set by the agency's harshest critics. The information advantage alone explains why he would never do that. He also probably does not believe that the NSA's motives are synonymous with descending fascism.

Instead, he probably has a modest set of goals. He will properly hand to Congress many of the larger decisions, which will be good for the debate, if not for the outcome. I think Congress is more susceptible to the public's anger about the NSA, at least in terms of near-term policy changes.

He will focus, I think, on the puzzle of metadata. Its collection can be incredibly valuable, but its analysis can be incredibly, potentially harmful. Metadata will always be produced by everything we do. We are walking emitters. Obama will not do anything to fundamentally constrain the NSA's ability to collect and analyze the metadata it needs to in order to fulfill the core intelligence requirements that the executive branch sends down. That's a hard line. Metadata, because of its indirect relationship to words we speak or write, and its direct bearing on activity, past and present, is a Gordian knot. Who keeps the data, for how long, and what they can and can't do with it, and why are questions that Congress will address, but I hope they are balanced by a commitment to provide real information to people about these processes, even with the certain risk of making it marginally easier for bad guys to know this, too.

Another puzzle I hope he addresses is encryption. The more the NSA works to make sure that it can crack the codes developed to protect information, the more easily it has also worked to undermine common standards of information security that provide real protection for valuable content and the feeling of protection from those who have the powers to watch us create, buy, sell, interact, and communicate. The more secure the world information grid is, the harder it is for the NSA to spy on it.

The less secure it is, the easier it is for the NSA to gather intelligence. It is a hard problem, too, but I hope the president chooses to recommend changes that err on the side of not intervening to surreptitiously weaken or create backdoors for encryption standards. The NSA will have to work harder to break codes, but if America truly champions strong global encryption that works, the public benefit will be tangible. It will be harder to steal stuff online. And we do almost everything online now.

And of course: I do not expect Obama to praise Edward Snowden, nor do I suspect he will offer any sort of sympathetic words for people who steal state secrets.