Seems unlikely that the legal arguments presented will stand up to public legal scrutiny. I'm certainly not a lawyer. However, as I read the cited comments about weighing private vs government interests, the cited commentary doesn't appear to suggest that due process can be denied altogether. Rather, the commentary appears to discuss practical issues of war that might have the effect of delaying due process.
Conveniently, the Obama administration lawyers failed to comment on the legal motivation behind the Bush era Guantanamo prisoner military trials. Namely, federal courts ruled that these prisoners had due process rights even though they were enemy combatants and despite the fact that they were not U.S. Citizens.
Both the dates of the legal opinions and news reports describing the Obama administration legal review process clearly show that the Obama administration had ample time and opportunity to engage in judiciary. They just chose not to do so, apparently. Given this, the al Qaida dirtbag's constitutional right to due process was trampled.
Personally, I have 0 sympathy for al awlaki, but clearly Obama signed off on an executive branch doctrine of extra judicial execution of American citizens that could be used to kill just about any American overseas. Asserting that a person is a member of a terrorist group and using that assertion as justification for that person's execution without providing external review and due process is nothing short of tyranny. Granted, if Obama had to violate some American's rights, he probably picked the right person.