Recently the Supreme Court of Canada, which does not operate like the SC of USA, ruled that assisted suicide is legal. The Charter states in section seven, "Everyone has the right to life, liberty and security of the person and the right not to be deprived thereof except in accordance with the principles of fundamental justice." This is the principle of which Mary Wagner argues that she has the right to approach pregnant women in order to encourage them to keep their babies. She argues that to deprive the unborn the right to life violates the Charter and as such she has the right to defend them. So far the justice system disagrees. In fact the SC or C recently ruled that euthanasia doesn't apply to the charter because while everyone has the right to life this does not mean that they are obligated to stay alive if they do not wish (forgetting the portion that says a right that cannot be deprived would include being deprived of life from a physician).
All of this of course hinges on society's notion of mercy killing. Mercy killing basically means to kill someone with the intention of relieving them from pain particularly if their death is imminent. The Catechism teaches that one doesn't need to use extraordinary measures in order to stay alive, but mercy killing is contrary to our faith. Euthanasia is one of those un-debatable things of the Catholic Church. You can't be a faithful Catholic if you think mercy killing is acceptable.
Mercy killing seems to permeate all aspects of society including children's books. Recently I got into a discussion about the Harry Potter books. One of my qualms with the books is the fact that Dumbledore's murder is a mercy killing. Someone argued that it might actually be part of Just War Doctrine, so let's look at why I don't think that is the case.
Here is the reasons why Dumbledore asks Snape to murder him:
1) He would be giving an old, ailing man dignity in death.
2) He would be preserving Draco Malfoy's soul.
The first reason is obviously a form of euthanasia. There's nothing dignified by murdering someone who is sick. We are called to heal a person as much as we can (which is why I don't understand why Fawkes the Phoenix doesn't donate his healing tears). We are to make their end as dignified as possible. Draco doesn't know this. He's charged with Dumbledore's murder without knowing about the illness. But Snape also is asked to murder Dumbledore knowing he's dying.
The second is definitely not Just War Doctrine because that involves a group of people as in a nation defending themselves from an aggressor. Dumbledore isn't an aggressor. He's also not a casualty of war since he's killed willfully by a friendly.
Is it Dumbledore defending himself or someone else? Neither is Dumbledore standing in Voldemort's way to prevent Draco's death. He's essentially depriving Draco from deciding between murdering him or not. He stands there trying to convince Draco not to kill him. Dumbledore has done his part. He's defending himself, but he's not really defending Draco. Draco has free will and if he decided to murder Dumbledore, yes he would have ripped his soul apart (until he confessed and sought forgiveness). Instead he does something bizarre by having Snape do so because of the first part.
Is Snape defending Draco? No. Because by Draco not killing Dumbledore as Draco was commanded by Voldemort, Draco runs the risk of still being killed. Voldemort is not known for being merciful when his commands aren't carried out. It's also worthy to note that Dumbledore doesn't ask Snape to defend Draco from Voldemort. Draco's mother does, but her request isn't really defense because she's not asking Snape to kill Draco's aggressor, which is Voldemort.
Is Snape defending himself? No. He made an unbreakable vow, which can kill you. The premise was that if Draco doesn't kill Dumbledore then Snape will. He shouldn't have made a vow. Even undercover cops cannot legally kill people to preserve their cover because it's still murder. That's where the moral problem truly lies. My understanding is that you can defend yourself even if you know someone will die. This may be because your aggressor is trying to kill you or because the person is an innocent bystander who the aggressor murders during your defense. Dumbledore isn't the aggressor; Snape is. So Snape's not defending himself from Dumbledore. Voldemort isn't trying to kill Snape; neither are the death eaters. Remember they think he's loyal to them.
So who's Snape really defending himself from? Nobody. He's trying to cheat himself out of death. Snape's plight reminds me of people whose doctor tells them if they have one more smoke, drink, or hit, they will die. Snape's put himself in danger but not from a person. So he can't really defend himself.
That's why I think this is a case of mercy killing not self-defense or defense or Just War Doctrine.