In the national security speech Obama delivered this afternoon, the President himself defined the challenge we face as this: How do we balance the need to do all we can to protect our citizens with the need to adhere to our values and ideals as a free society? The speech was the most ambitious and detailed effort to answer this question that he has yet attempted.

His answer to the question was that, at a time when the nature of the terror threat is changing — over a decade after the 9/11 attacks led to a massive buildup of our national security apparatus that strayed into massive overreach – we must acknowledge the cost of all of that excess, and give more priority to American values and the rule of law than we have been giving. However, in policy terms, he offered mainly incremental, though welcome, moves in that direction.

Indeed, the upshot of the speech is that Obama defined his own role — that of commander in chief — as one that requires him to ultimately compromise core values and principles if he deems it necessary to maintain security. While the speech did offer some steps that civil libertarians will welcome, it also fell short of the wholesale commitment to rule of law they had hoped for — indeed, forthrightly so.

This was the common thread that ran through his discussion of the two most controversial national security debates of the moment: Drone strikes, and Guantanamo. As Mark Jacobson, a senior adviser to the center-left Truman Project put it to me, Obama’s speech was less a substantial break from current policy than it was a newly ambitious effort to recalibrate policies on drones and the detention of terror suspects with the specific goal of reconciling them with American values. “This is really an evolution,” Jacobson said.

On drones, Obama took several welcome steps. He said his administration had produced a new Presidential Policy Guidance that codify guidelines, oversight and accountability (though the details will matter). He said he’d tightened up the criteria the targets must meet — they must post a “continuing and imminent threat,” while there must be “near certainty that no civilians will be killed or injured.”

However, he flatly defended the use of drones, even though they pose a risk to civilians, arguing that other methods of going after their targets pose a greater risk, to civilians and international relations alike. And he flatly stated that the role of “commander in chief” effectively requires him to continue running the risk of civilian deaths when he deeps it necessary for national security reasons. He claimed the authority to target a U.S. citizen abroad — without due process, presumably — on the same grounds. “These decisions must be made, given my responsibility to protect the American people,” he said — implicitly prioritizing security in the end above all as necessary to his role.

On Guantanamo, also took several welcome steps. He again demanded Congress close the prison, lifted the moratorium on detainee transfers to Yemen, vowed to step up other transfers, and said he’s appointing a new envoy tasked with speeding them. He stated flatly that holding people “charged with no crime” is incompatible with American values. At the same time, he seemed to suggest that indefinite detention will continue in the near term, albeit on American soil, claiming he has asked the Department of Defense to find a site in the United States for military commissions. He noted that the core problem — the need to hold those who “have participated in dangerous plots or attacks, but who cannot be prosecuted” — will “remain,” though he predicted it would be resolved later.

Indeed, the entire speech seemed threaded with an implicit concession that in the end, the perfect balance between maintaining security and rule of law may not quite be achievable. For this reason, civil libertarians are finding it ultimately wanting, even if they see some of the steps Obama took as positive ones.

“The president is clearly aware that his current policies are falling short of the mark constitutionally,” Anthony Romero, the executive director of the American Civil Liberties Union, told me. “While these are important and welcome steps, they are incremental changes that pale in the face of the constitutional questions confronting the administration.”

Obama might agree to some degree with that assessment, with a qualifier. Indeed, the speech seemed quite forthright in defining the role of commander in chief as one that requires him to ultimately prioritize security over strict rule of law where he deems it necessary — even as he implicitly asked us to trust that he’s doing his best to get the balance as close to right as he can.

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.