Ken Anderson and Ben Wittes, in their online book, Speaking the Law: The Obama Administration’s Addresses on National Security Law (2013), have selected and analyzed 13 speeches by the President and others in his administration:

OVERVIEW

Over the course of President Obama’s first term in office, the president and senior officials of his administration have given a series of major speeches on the legal framework for confronting terrorists overseas. The speeches collectively represent the fullest statement the administration has given of the law of drones, targeted killing, and the larger approach to the war against Al Qaeda and its allies. The Obama administration has faced criticism both for the content of the speeches and for not saying more in them–and releasing the legal memos that lie beneath them. In Speaking the Law, Kenneth Anderson and Benjamin Wittes dissect the Obama administration’s major speeches on national security law–analyzing what the administration has actually said, fleshing out the virtues and vices of the legal framework it has mapped out, and suggesting areas for legislative refinement and further administration development.
Those "canonical" speeches involve policy and strategy as much (or more) than "down in the weeds" legal issues.

The outline of the online book (to be published in stages) is:

Speaking the Law (Introduction), by Kenneth Anderson and Benjamin Wittes [19 pp.]

Speaking the Law (Chapter 1), by Kenneth Anderson and Benjamin Wittes [64 pp.]

Speaking the Law (Chapter 2), by Kenneth Anderson and Benjamin Wittes [64 pp.]

[JMM: Chapters 3, 4 & 5 to be published later]

Appendices A, B & C: Addresses and Remarks by President Obama and Administration Officials on National Security Law [JMM: at over 160 pp., has extensive snips of the full speeches]
For those who want the complete speeches, here they are:

President Barack Obama, “Remarks by the President on National Security,” The National Archives, Washington, D.C., May 21, 2009

President Barack Obama, “A Just and Lasting Peace,” the 2009 Nobel Peace Prize Lecture, Oslo, Norway, December 10, 2009

Harold H. Koh, legal adviser to the Department of State, “The Obama Administration and International Law,” address to the American Society of International Law, Washington, D.C., March 25, 2010

Harold H. Koh, legal adviser to the Department of State, “International Law in Cyberspace,” address to the USCYBERCOM Inter-Agency Legal Conference, Fort Meade, Maryland, September 18, 2012

David Kris, assistant attorney general for national security, “Law Enforcement as a Counterterrorism Tool,” address at the Brookings Institution, Washington, D.C., June 11, 2010

Jeh C. Johnson, general counsel, Department of Defense, “U.S. Terrorist Suspect Detention Policy,” speech to the Heritage Foundation, Washington, D.C., October 18, 2011

Jeh C. Johnson, general counsel, Department of Defense, “National Security Law, Lawyers, and Lawyering in the Obama Administration,” address at Yale Law School, New Haven, Connecticut, February 22, 2012

Jeh C. Johnson, general counsel, Department of Defense, “The Conflict against Al Qaeda and Its Affiliates: How Will It End?” Oxford Union, Oxford University, November 30, 2012

Eric Holder, attorney general, Department of Justice, "Address at Northwestern University School of Law", Chicago, Illinois, March 5, 2012

Stephen W. Preston, general counsel, Central Intelligence Agency, “CIA and the Rule of Law,” address at Harvard Law School, Cambridge, Massachusetts, April 10, 2012

John O. Brennan, assistant to the president for homeland security and counterterrorism, “Strengthening Our Security by Adhering to Our Values and Laws,” address at Harvard Law School, Cambridge, Massachusetts, September 16, 2011

John O. Brennan, assistant to the president for homeland security and counterterrorism, “The Ethics and Efficacy of the President’s Counterterrorism Strategy,” Woodrow Wilson International Center for Scholars, Washington, D.C., April 30, 2012

John O. Brennan, assistant to the president for homeland security and counterterrorism, “U.S. Policy toward Yemen,” Council on Foreign Relations, New York City, August 8, 2012.
- cont. in part 2