The question of Presidential "power to make war" vs Congressional "power to declare war" - and pay for "war" - has come to the fore in many venues since the last post to this thread in 2008.

Recently, Curtis Bradley has joined the Lawfare Blog. Bradley has partnered in a number of projects with Lawfare's Jack Goldsmith (who headed up OLC during a portion of the GWB WH). Bradley has submitted two short posts (each about 2 screens) dealing with "War Powers":

Historical Practice in the War Powers Debate

Historical Practice and the “Intermediate” Position on War Powers

The first step is to read those two posts. They provide a general overview of the three views of "War Powers": a pro-Congress view; a pro-Executive view; and an “Intermediate” Position.

The next step is to go to the War Powers Resolution of 1973 and just read it to get its basic structure. Don't dwell on it too long - because it is not really definitive for any of the three positions (from Bradley's 1st article):

Supporters of both the pro-Congress view and the pro-Executive view invoke the War Powers Resolution of 1973, but its implications for any sort of shared understanding are unclear.

On the one hand, it states in Section 2 that the President has the authority to use force only upon either “(1) a declaration of war, (2) specific statutory authorization, or (3) a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.”

On the other hand, presidents have indicated at various times that they do not agree that this is a correct description of the Constitution.

Section 5 of the War Powers Resolution calls for termination of presidential uses of force after 60 days unless approved by Congress, which might suggest that Congress accepts the constitutionality of presidential uses of force of shorter duration.

On the other hand, it may simply suggest that Congress compromised on the remedy it mandated for illegal operations, especially if this section is read in conjunction with what is stated in Section 2.

Finally, Section 8 of the Resolution states that the authority to use force shall not be inferred from treaties.

On the other hand, presidents have subsequently relied on treaties as partial justification for the use of force, including in the Libya campaign.
So, the War Powers Resolution is akin to "Fiddler on the Roof", where one argues back and forth from one hand to the other hand - until one concludes there is no other hand.

Having that background, next turn to the current OLC opinion on Libyan operations (OLCM 1 Apr 2011) - BLUF:

This memorandum memorializes advice this Office provided to you, prior to the commencement of recent United States military operations in Libya, regarding the President’s legal authority to conduct such operations. For the reasons explained below, we concluded that the President had the constitutional authority to direct the use of force in Libya because he could reasonably determine that such use of force was in the national interest. We also advised that prior congressional approval was not constitutionally required to use military force in the limited operations under consideration.
Take this as a brief - not an impartial opinion (no specific criticism of the Obama admin on this point; GWB had John Yoo et al).

This is not a "pure" pro-President brief (e.g., such as John Yoo's efforts); and it certainly is not "pro-Congress". Bradley critiques it and the "Intermediate" postion as follows (2nd article):

The intermediate position contends that, although the President may need congressional authorization to initiate “significant” or “real” wars, he need not obtain authorization for “lesser” or “limited” military operations.
....
There are three major problems with the intermediate war powers argument. First, as discussed in my last post, we have no strong evidence that the instances in which presidents have initiated the use of force without congressional authorization, whether in “limited” operations or not, have reflected any shared understanding between Congress and the President over the distribution of war authority. Some operations, such as in Panama or Grenada, may reflect only an understanding of a presidential authority relating to self defense or the rescue or protection of U.S. citizens, an authority typically accepted by those advocating the pro-Congress view of war powers. Other operations, such as the one in Kosovo, were conducted in the face of substantial congressional resistance, or eventually triggered constitutional complaints in Congress, as in Somalia. In other instances, it is likely that the lack of congressional opposition was merely ad hoc and tactical and did not reflect any general constitutional concession.

Second, the line between “limited” and “real” wars is highly uncertain and thus subject to substantial manipulation by the President. The duration and scope of military campaigns are almost always unpredictable and have a tendency to expand, as is becoming evident once again in Libya — for example, with the recent announcements that the United States is going to begin using armed drones there, and that other countries are placing military advisers on the ground. Indeed, even some of the conflicts that advocates of the intermediate position concede to be “real” wars, such as in Vietnam and Afghanistan, have started as more limited military campaigns.

Finally, the clearest articulation of Congress’s view on the question of what constitutes a significant enough commitment of forces to require congressional authorization is contained in the War Powers Resolution of 1973, which was enacted in the wake of the Vietnam experience. That Resolution refers to all situations involving the “introduction of United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances.” Operations like the ones in Kosovo and Libya clearly qualify under this standard.
A more complete critique of the 1 Apr 2011 OLCM is found in Glennon, The Cost of “Empty Words”: A Comment on the Justice Department’s Libya Opinion (14 Apr 2011, Harv. NSJ) (19 pp. in pdf). It covers these main areas:

I. Presidential War Power

II. Security Council Resolution 1973

III. The War Powers Resolution as Authorization
You may or may not agree with Glennon's arguments, but it is a good framework (we always can make additions) to present "War Powers" arguments.

A separate, but related, issue is the force of UNSC Resolutions on member states - mandatory or optional; self-executing or requiring approval at the national level - if approval is required at the national level, what constitutional process is required ?

For that, see Declaring War and the Security Council, by Michael Ramsey (28 Mar 2011) (Opinio Juris is a good I Law blog - it is not amateur week) - which answers the above questions, applied to UNSC Res. 1970 & 1973, as optional and requiring approval at the national level. Like Glennon, it presents a framework for analysis and presentation.

So many "AUMF" situations are presenting themselves now that reviving this thread seemed a better way to create a "War Powers" reference that can be cited from individual threads on conflicts.

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IMO: We all know that legal debates (whether sophistry or not) do not affect one fact of "armed conflict" - people die (both combatants and civilians). To the individual, the size and "legal characterization" of the "armed conflict" matter naught - nor, whether a President, Congress or me says it is or is not a "war". All the Sailors and Marines added up here were casualties - in "conflicts" big or small (from 1775 to 2002).

Whether we agree or not with the political policies that drive the "conflict", we all are responsible for sending our friends (then young men) into wars and some of them die (becoming "forever young" because that is the only way we as humans can remember them).

Regards

Mike