First off, I'd like to apologize - particularly to Red - for my recent absence from the blog. I have a number of explanations which do not really add up to an excuse.
I'm fascinated by the comments on Red's post on the Fifth Commandment. I'm particularly interested in the arguments that the State has an authority to act which goes beyond the authority of any of its members.
The State, in the examples given, has the authority to execute prisoners and to wage war. No mere citizen has that authority. A person only is able to execute or wage war upon another person when acting as an agent of the State.
Now, I'm not in any way an expert on politics, or even on political philosophy. But it's clear to me that "The State" had rather a different implication in the mind of St. Thomas Aquinas than it does for us today. Today, we generally assume a constitutionally founded, geographically defined, internationally recognized nation-state, with recognizable institutions for legislative and executive functions. Thomas could have had none of those assumptions. In his day, the State would have ranged from more-or-less independent city-states to feudal regions to monarchies, all of which argued (and even warred) over borders, relationships, and dues. Moreover, the Church had a more political profile in his day, arguing with civil leaders about the authority to appoint bishops and to crown rulers.
So, although I have the highest respect for Thomas's philosophy and theology, I would consider it a betrayal of his thought to simply accept his statements about the State and it's role and authority without further examination.
So I ask, what is the basis of the State's authority, from the standpoint of the Church? And then, what does this imply about the State's authority to act in such ways as, for example, to defend its borders or to execute criminals or to regulate migration?
For the record, I don't yet have answers to these questions. Nor do I expect that there is only a single form of government that would meet the requirements of Catholic moral teaching. And furthermore this may just plain be too abstract a topic for this policy-focused blog. But consider it an introduction, and feel free to give me pointers toward texts I might not have met yet myself.