Is Vengeance Forbidden?

In the discussion of the killing of Osama Bin Laden here (see below for various posts and comments), I have been struggling with the notion that the motivation/justification of vengeance seems to be categorically off the table -- an unequivocally forbidden reason for wanting to kill -- at least for Catholics, and perhaps for Christians generally.  Contemporary theories of punishment, to the extent that they are analogous (perhaps they are not), likewise generally disdain vengeance, preferring instead to rest on deontological or consequentialist bases.  It was not always so for theories of punishment -- and as some authors (e.g., Paul Robinson and John Darley) are finding out, popular ideas of retribution and vengeance are not so easy to disaggregate. 

But I've got a different question for MOJ readers.  For Catholics, is vengenace totally off limits?  I ask the question in all humility, as I genuinely don't know.  I anticipate that someone might cite Romans to me -- "'Vengeance is mine,' saith the Lord."  Fair enough -- but the admonition here seems to be not that vengeance is morally wicked (after all, it is God's) but that human beings should act with great caution when they are motivated by vengeance.  They ought to temper their vindictive instincts because they (unlike God) are not in an epistemic position to act purely from vindictive motives (cf. John 8:7).

Does that mean that human beings should repress totally the emotion of vengeance?  I have difficulty believing this. 

As Jeffrie Murphy points out in the book that I talked about below, vengeance is not inherently evil.  It is an emotion which is neither entirely good nor evil.  The vindictive passions are connected not only to self-respect but they also evince our commitment to and respect for the moral order: "Moral commitment is not merely a matter of intellectual allegiance; it requires emotional allegiance as well, for a moral person is not simply a person who holds the abstract belief that certain things are wrong.  The moral person is also motivated to do something about the wrong -- and the source of our motivation lies primarily in our passions or emotions."  (GE, 19).  Justice, after all, was in some way supposed to co-opt vengeance as a response to wrongdoing; but if justice did co-opt vengenace, does not vengeance, to some extent, continue to inform justice?

It is certainly true that permitting the vindictive emotions to dominate or control one's response to wrongdoing in whatever sphere would be dangerous.  But does that mean that allowing vengeance some place in that response is to be rejected outright?  And if so, why?  When news of bin Laden's death reaches Catholic ears, is it necessary to cast out of one's consciousness as utterly forbidden the notion that the passions of vengeance have been satisfied, and that it is proper that they be so satisfied?  

I am not remotely an Aquinas scholar, but St. Thomas says this (I've italicized the sections that might support some of my thoughts here, though I am deeply unsure and would welcome correction):

[V]engeance consists of the infliction of a penal evil on one who has sinned.  Accordingly, in the matter of vengence, we must consider the mind of the avenger.  For if his intention is directed chiefly to the evil of the person on whom he takes vengeance, and rests there, then his vengeance is altogether unlawful: because to take pleasure in another's evil belongs to hatred, which is contrary to the charity whereby we are bound to love all men . . . .

If, however, the avenger's intention be directed chiefly to some good, to be obtained by means of the punishment of the person who has sinned (for instance that the sinner may amend, or at least that he may be restrained and others be not disturbed, that justice may be upheld, and God honored), then vengeance may be lawful, provided other due circumstances be observed.

St. Thomas has further deeply interesting reflections on the place of vengeance at question 108 of the Secunda Secundae.  Thoughts on these issues from readers?