I can't answer the question asked (as the title of this thread) because I don't have the foggiest idea what rationales drive the Obama administration to do what they do.

I can say firstly the drone strikes (and implicitly all direct action taken against HVTs) are based on the Laws of War. See this post, A timely response from the Obama Administration, in the Drone Paradox thread. Just a snip from LA Koh's statement:

[I]t is the considered view of this administration…that targeting practices, including lethal operations conducted with the use of unmanned aerial vehicles (UAVs), comply with all applicable law, including the laws of war….As recent events have shown, Al Qaeda has not abandoned its intent to attack the United States, and indeed continues to attack us. Thus, in this ongoing armed conflict, the United States has the authority under international law, and the responsibility to its citizens, to use force, including lethal force, to defend itself, including by targeting persons such as high-level al Qaeda leaders who are planning attacks….[T]his administration has carefully reviewed the rules governing targeting operations to ensure that these operations are conducted consistently with law of war principles, including:

- First, the principle of distinction, which requires that attacks be limited to military objectives and that civilians or civilian objects shall not be the object of the attack; and

- Second, the principle of proportionality, which prohibits attacks that may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, that would be excessive in relation to the concrete and direct military advantage anticipated.

In U.S. operations against al Qaeda and its associated forces – including lethal operations conducted with the use of unmanned aerial vehicles – great care is taken to adhere to these principles in both planning and execution, to ensure that only legitimate objectives are targeted and that collateral damage is kept to a minimum.…
Both legal and practical aspects are covered more fully in this thread, HVTs/Political Assassination, and its many links.

I can say secondly that our detention policy is also firmly based on the Laws of War - e.g., take a look at these posts in the War Crimes thread (all on page 12):

222 - Obama DoJ "refines" the standard for detention !!

223 - Statements about the new standard ...

225 - DoJ Memorandum re: detention

226 - continuation of DoJ memo ...

227 - Well, George, if you are asking my opinion on this ...

The key statement in this package is from #226:

Moreover, the Commentary to Additional Protocol II draws a clear distinction between individuals who belong to armed forces or armed groups (who may be attacked and, a fortiori, captured at any time) and civilians (who are immune from direct attack except when directly participating in hostilities). That Commentary provides that “[t]hose who belong to armed forces or armed groups may be attacked at any time.” See ICRC, Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 Aug. 1949 and Relating to the Protection of Victims of Non-International Armed Conflicts (Additional Protocol II), ¶ 4789.
(emphasis added). Thus, both direct actions and detentions have the AUMF as their base and are clearly based on the Laws of War.

The Rule of Law (domestic laws, whether in the US or in foreign countries) has nothing to do with either direct actions or detentions.

How did the Rule of Law get into this discussion ? Because folks in the Bush II and Obama administration wanted, or felt it necessary, to go beyond detention and prosecute crimininally. The criminal prosecution approach (going back to the Clinton administration) could go either of two routes: military commissions (Bush II prime choice) or Federal courts (Obama prime choice). In either, the procedures (due process) are spelled out.

Regards

Mike