That's the title of this 1994 article in The Wanderer (ht: Raving Papist) by moral theologian Charles Rice, long-time professor at Notre Dame Law School and author of Fifty Questions On Natural Law: What It Is and Why We Need It.
The very short answer is, "No!"
Dr. Rice wrote, in part:
In self-defense or defense of others, against an aggressor, the intent must be to defend, rather than to kill. Consider two situations. In the first, Able, an abortionist's assistant in the killing room, suddenly has a change of heart moments before the abortion begins. He has a right and even a duty to use force to defend the child, not to kill the abortionist. In the second situation, Baker, an opponent of abortion, shoots the abortionist in the parking lot as he is approaching the building to do abortions a few minutes later.
One difference between the two cases is imminence. Able engages himself in the immediate defense of the child; he has no intent but to defend that child; he has no separate intent to harm or kill the abortionist. Recall that, in justified self-defense or defense of others, the intent cannot be to kill the aggressor, but rather to stop the attack. Baker, by contrast, is not in the heat of a physical struggle to save the child. He thinks, "I can get no closer than this. If I do not stop him he will go in there and murder babies. So I will shoot him in the head." His purpose or motive is to save children. But his intent in the act he performs that moment is to blow the baby killer's head off in order to achieve that purpose of saving children. Apart from the just war, capital punishment, or the justified rebellion, which derive from the authority of God, no one may ever intentionally kill anyone. Baker is intentionally doing an intrinsically evil thing to achieve a good end. He assumes the authority of God, to decide when that person will face the final judgment of God. His act cannot be justified. St. Thomas, quoting St. Augustine, said that "`a man who, without exercising public authority, kills an evildoer, shall be judged guilty of murder, and all the more, since he has dared to usurp a power which God has not given him"' (Summa Theologiae, II, II, q. 64, art. 3).
Some may argue that killing the baby killer in the parking lot is defense of the child because that is as close as Baker could get. But if Baker may kill the abortionist when he is not actually performing an abortion, why does he have to limit himself to the parking lot? Why can he not conclude that the only practicable way he can get a clear shot at him is to shoot him on the golf course? Or at the video store? St. Thomas speaks of the justified defender as one who "repels force." See the Catechism, N. 2264. Unless we are to declare open season on abortionists, so as to justify their intentional execution by anybody so inclined wherever practicable, the right to defend the child must be restricted to the immediate performance of the abortion. Even then it is practically inconceivable that lethal force would have to be used.
The first of the above two examples is academic, because opponents of abortion, practically, do not find themselves in abortuary killing rooms. The issue is simply whether it is justifiable to kill abortionists, wherever and whenever an opportunity to do so presents itself.
The intentional killing of an abortionist could be justified only if it were incidental to a justified rebellion, which would itself be a just war, in which the abortionist was rightly regarded as a combatant and therefore a legitimate target. However, "Armed resistance to oppression by political authority is not legitimate unless all the following conditions are met: 1) there is certain, grave, and prolonged violation of fundamental rights; 2) all other means of redress have been exhausted; 3) such resistance will not provoke worse disorders; 4) there is well-founded hope of success; and 5) it is impossible reasonably to foresee any better solution" (Catechism, N. 2243; emphasis in Catechism). These criteria do not justify the intentional killings of abortionists. Michael Griffin was not resisting an immediate, unjustified attack by the Bureau of Alcohol, Tobacco, and Firearms. By no stretch of the imagination can one reasonably conclude that we are in an insurrectionary situation in the United States today such as to justify his intentional killing of a person who was not then attacking anyone. A justified rebellion involves the assumption by private persons of the prerogative of the state to wage a just war. In a rebellion the war is waged against the state itself. In Roe v. Wade, and later cases, the Supreme Court, with the cooperation of Congress and the Executive Branch, has precipitated an unraveling of the American civic fabric. It cannot, however, be legitimately concluded that the situation has disintegrated so far beyond other means of correction that armed rebellion is justified in whole or in part.
Rebellion, incidentally, is not something to be lightly sanctioned. The just war waged by a government has the limiting feature that it can be waged only by the duly constituted public authority. A rebellion, by contrast, involves an assumption of all or part of that public authority by private persons who themselves decide that they are justified in taking over the power of the state in whole or in part. And if one can so decide, so can another. In Populorum Progressio, in 1967, Pope Paul VI said that "a revolutionary uprisingþsave where there is manifest long-standing tyranny which would do great damage to fundamental personal rights and dangerous harm to the common good of the country produces new injustices, throws more elements out of balance, and brings on new disasters. Real evil should not be fought against at the cost of greater miseries (Populorum Progressio, N. 31).
Definitely read the entire essay.
Already, within the span of a few hours, a standard line by some abortion supporters/providers has become, "Those who call abortion murder are implicitly or indirectly responsible for Tiller's death." It's a nifty bit of rhetoric, but one that is inherently flawed. It rests on the very shaky premise that if you believe someone has committed murder, you will be inclined to kill them if you have a chance. But both logic and experience say otherwise. The vast majority of people—even those with intense emotions about the matter—seek justice through lawful means, even if those means are often frustrating and, in some cases, deeply flawed. The vast majority of Christians rightly recognize that murdering a murderer is not only a false solution, it is an evil one, as Dr. Rice explains very well in his essay. The statement, "Abortion is murder," is either objectively true or false; how someone chooses to act based on that statement can be either lawful or unlawful, good or evil.
(By the way, what of the matter of those liberals who have accused George W. Bush of being a murderer? Shouldn't they be considered hate-mongers who are potentially inciting acts of violence? Or what of those who say the Catholic Church is responsible for the death of thousands in Africa because it opposes the use of contraceptives?)
This disingenuous rhetoric of convenient blame is used because abortion supporters (oops, I mean reproductive justice advocates) know who it is resisting the mythology of a Brave New World built on contraceptives, abortion, euthanasia, fornication, and "gay marriage." And the best way to undermine and even destroy those folks is to portray them en masse as domestic terrorists, religious extremists, and lawless theocrats. Trying to portray everyone in the pro-life movement in such a way is aided greatly by the slaying of Tiller. The fact that the act was immediately condemned by numerous pro-life groups and leaders is either ignored or described as "hypocritical," as if it is somehow impossible to accurately describe abortion and then peacefully work to end it.
In the hours and days immediately following 9/11, a host of moderate Islamic groups loudly denounced the attacks, and Americans were assured by the media and the government that the horrific events had nothing to do with true Islam. What's that? You don't remember the many statements by moderate Islamic groups? Well, regardless, you surely remember being told—even by President Bush—that Islam is a religion of peace. Surely the same benefit of the doubt will be extended to pro-life groups, won't it? Won't it? No? Of course not. Such are the deep and difficult challenges facing those staring into the darkness of the culture of death.
You play by the rules and do the right thing the right way and yet you are portrayed as narrow-minded, violent, hateful religious nuts. So imagine what happens when a violent, hateful nut (apparently a "Christian" of some sort) murders an abortionist? Well, unfortunately, we don't have to imagine. Mark Shea laments, "In our present cultural climate, it is quite possible that the man who did this just murdered the pro-life movement." I'm not ready to go so far, but I understand where he is coming from.
The Curt Jester has a good compilation of statements about Tillman's death and what it might mean for the future of the pro-life movement.