This is rather begging the question by defining the issue as justiciable from the outset, in similar fashion to the religious argument that 'the existence of creation implies a creator, therefore God exists.'
It's my view that the pursuit of military objectives is very much the province of the executive, and that the elimination of Anwar Al-Awlaki was an entirely legitimate military objective since Al-Awlaki was (at the least) involved in rallying supporters to his cause and exhorting them to kill Americans, and arguably directly involved in the planning and authorization of such operations, exactly the sort of threats the Executive branch is responsible for addressing.
It's my view that the pursuit of military objectives is very much the province of the executive, and that the elimination of Anwar Al-Awlaki was an entirely legitimate military objective since Al-Awlaki was (at the least) involved in rallying supporters to his cause and exhorting them to kill Americans, and arguably directly involved in the planning and authorization of such operations, exactly the sort of threats the Executive branch is responsible for addressing.