This article primarily addresses the Political (including Diplomatic) Considerations, with lesser emphasis on the Military Considerations. It does address Legal Considerations to some extent (pp.11-14 pdf).

Here are some excerpts - the first dealing with the "lawyerly consensus":

Lawyers by consensus regard transnational terrorism as a transgression falling uneasily between the cracks of traditional criminal law and the customary law of armed conflict, and targeted killing as a punitive remedy falling just as discomfitingly between the cracks of those two legal regimes as well as international humanitarian law. For basically pragmatic and prudential reasons, they are generally willing to accept that targeted killing is not tantamount to government-sanctioned political assassination, which has run counter to US policy since 1976 (In that year President Gerald Ford issued Executive Order 11905 barring assassination, after revelations of CIA attempts to assassinate several heads of state, notably Cuban leader Fidel Castro.[15]) They also concede the reality that full due process cannot always be afforded terrorists owing to the immediate threat some pose, and the operational impracticality of subjecting purportedly actionable intelligence to quasi-judicial review in very tight time frames.[16] But a level of indiscriminateness that claims civilian casualties at an order of magnitude higher than legitimate ones is not only dubious in ethical and humanitarian terms, but may also be politically counter-productive. On this issue, the laws of armed conflict broadly apply, and they require that the use of military force be necessary, as a matter of self-defence, to eliminate a genuine threat and that it be reasonably proportionate to that threat.

15 The prohibition has been skirted in a number of instances by means of military ‘leadership strikes’ targeting political leaders, such as the US bombing of Libya in 1986, which clearly targeted Libyan leader Muammar Gadhafi, and the opening salvos of the Iraq War in 2003, which were unabashedly intended to kill Iraqi President Saddam Hussein.

16 See, for example, Kenneth Anderson, ‘Targeted Killing in U.S. Counterterrorism Law and Strategy’, A Working Paper on Counterterrorism and American Statutory Law, a Joint Project of the Brookings Institution, the Georgetown University Law Center, and the Hoover Institution, 11 May 2009, pp. 9-12; http://cryptome.org/kill-lawyers.pdf.
The last cited "kill-lawyers.pdf" (if literally true) would give a new, modern meaning to Shakespeare and targeted killings.

The fact is that there is no lawyerly consensus. The view represented by the Eminent Jurists Panel excludes the Laws of War from application to TVNSAs. The view of some in the US (e.g., some Fox News pundits) is that the Rule of Law has no place in this arena under any circumstances. Then we have Lawyer Stevenson (JD Boston University) who seeks to meld the Laws of War and Rule of Law in an acceptable fruit salad.

Then there is my view (which is not a datapoint of one) which looks at this arena as one in which concurrent jurisdictions apply in many cases. In short, the Laws of War and the Rule of Law may both apply to the same individual who is a TVNSA combatant. However, while that approach allows two options to be pursued, the courses of action differ depending on whether the military or civilian paths are followed. You can't mix the two systems without failure.

Simon-Stevenson (after some policy discussion) then point out some practical issues:

The legality of targeted killing remains hotly contested between the national governments with the standoff targeting capabilities and humanitarian lawyers who view it as an evasion of at least three legal regimes and a practice which, if endorsed by law, raises the incentive to use force rather than resort to law to a dangerous and uncivilised degree.[18] This debate will take time to resolve. But it seems safe to say now that, based on considerations of criminal law, international humanitarian law and the law of armed conflict, and from a moral as well as a legal standpoint, the only arguably acceptable substitute for due process in the context of targeted killing is a combination of accurate intelligence, assiduous target selection that prioritises minimising civilian casualties, and technically precise targeting. Review processes have been established for both assessing the accuracy of purportedly actionable intelligence and determining the feasibility of targeting a given terrorist with a minimal probability of harming innocent civilians.[19] But the details of the procedures used and the level of scrutiny applied remain essentially secret, and certainly closely held by the US military and the CIA.[20] Moreover, these procedures are reportedly routinely disregarded in the field, where mid-level operational commanders or CIA officers sometimes order drone strikes without higher approval.[21] Finally, fears about the integrity of targeted-killing operations have arisen from disclosures that disreputable private military contractors have been hired to deploy missiles on Predators.[22]

19 See, for example, Eben Kaplan, ‘Backgrounder: Targeted Killings’, Council on Foreign Relations, March 2006, http://www.cfr.org/publication/9627/.

20 See Hina Shamsi, ‘No Longer A Debate About Targeted Killings’, CBS News, 21 July 2009, http://www.cbsnews.com/stories//2009...n5176876.shtml.

21 See David Montero, ‘Use of Drones in Pakistan and Afghanistan: Deadly, but Legal?’, Christian Science Monitor, 12 August 2009, http://www.csmonitor.com/2009/0812/p99s01-duts.html; Rajiv Chandrasekaran, ‘Sole Informant Guided Decision on Afghan Strike’, Washington Post, 4 September 2009m p. A1.

22 See James Risen and Mark Mazzetti, ‘C.I.A. Said to Use Outsiders to Put Bombs on Drones’, New York Times, 20 August 2009.
Note that the authors have reached the conclusion that there is "only [one] arguably acceptable substitute for due process" - "due process" being a Rule of Law concept. The solution therefore is a collage "based on considerations of criminal law, international humanitarian law and the law of armed conflict."

That fruit salad becomes more apparent as we reach the conclusion of the "legal section":

Accordingly, some balance between procedural transparency and substantive secrecy ought to be achievable, and the administration should try to strike it. Greater accountability would tend to engender a more rigorous targeting-review policy and could, perforce, lead to fewer civilian casualties. American analyst Daniel Byman, looking at the Israeli experience, has outlined sensible procedures for assessing the operational validity of targeting particular individuals.[24] There is no obvious reason that a review process similar to the one he has described, involving sequential consideration up the military and civilian chain of command, then a legal review by a Justice Department official, and finally a judgment by a special court modelled on the statutorily created Foreign Intelligence Surveillance Act court, could not be systematically imposed across a wider range of target-selection criteria, including the likelihood of collateral damage.
The bolded text is sheer lunacy - it makes the micro-management of direct actions, which we have seen leading to failures, pale in comparison - "sequential consideration up the military and civilian chain of command, then a legal review by a Justice Department official, and finally a judgment by a special court."

From a legal standpoint, I would hope that a majority of SCOTUS would declare this unconstitutional cuz (1) the matters are assigned to the executive and legislative branches and outside the purview of Article III; (2) except for TVNSA combatants within the US (as defined in the Gitmo cases), the matters are beyond the territorial jurisdiction of Article III courts; and (3) the matters do not constitute a "case or controversy" and constitute advisory opinions. With some more thought, more arguments probably could be developed.

Now, from a military standpoint, could you military types tell me what is wrong with "sequential consideration up the military and civilian chain of command, then a legal review by a Justice Department official" ?

I don't like mixtures of apples and oranges, which the Simon-Stevenson article is (IMO - others may differ).

Regards

Mike