To answer this question, let's look at what the "Book of Spirits" tells us in Chapter 6 of the Law of Destruction, Murder:
Is murder always the same degree of guilt?
- We have already said it: God is just, he judges intention more than fact.
As far as murder is concerned, the fault is in accordance with the fact, meaning that not all pay the tribute of their deeds with the same intensity, because it takes into account their feelings.
In question 748 of The Book of Spirits, specific in regard to self-defense, Kardec asks: Is there justification for murder in the case of self-defense before God?
"Only necessity can excuse you." But if the assailant can preserve his life without attacking that of the aggressor, he must do so. Therefore, only the need to act, based on the impossibility total to preserve life without attacking the life of the aggressor, is that it has the divine excuse. The level of guilt, in the case of self-defense, is less, if compared to a crime practiced by evil and that could be avoided; because in the first case, there is an attenuation; already, in the second, no. Certainly, spirituality did not want to be radical, however, in a strictly Christian view not even in legitimate defense could be killed. From a radically Christian and spiritualist point of view, it is better to receive death than to impinge it on someone.
The one who kills, even in legitimate defense, uses violence against the aggressor and violence may have mitigating factors, but it is always an attempt on life and divine law. Conservation Law. Whoever murders does not know divine laws well; after he comes to know that he is, in a way, killing his possibilities of growing or retarding them, he changes his mind, preferring to preserve the lives of his brothers. The Miramez Spirit, commenting on question 748 of the Book of Spirits, tells us:
"We must not confuse the law of God with the laws of men, for in the law of God there is no self-defense. This is men's recourse to alleviate their crimes. They themselves, the creators of the laws, of so much evil that they do to the collectivity, are looking for a preventive for their faults.
... If someone attacks us, it is certainly because we attack someone. If repentance already vibrates in our minds and hearts, let us seek the means of defense before evil happens. Let us surrender ourselves to love, to all and to all, that the rest will come by an increase of mercy. God is everywhere, as well as in the aggressor, charging and teaching the battered that all and all are children of the same God. ... It is not right to retaliate against the aggressor; it is being an instrument of the collection of what has already been done; is not to equate to it not to become an aggressor as well. As for self-defense, the true paths are with Jesus: when hatred comes to meet us, let us create a legitimate defense with love; if the violent attack us, let us forgive, forgetting the fault; if someone steals us, let us pray for him, without the Spirit of vengeance. Let us strive to be honest in everything we do and think, because life, as we know it, repays us what we give to others.
... It is not given to us to do justice with our own hands. We must do everything that our hands are not stained with our brother's blood. ... Every murderer responds by his act against his brother. The scale of guilt is enormous, however, killing is always a grave fault, because only the one who gave life can take it when it is convenient. ... If we want to be free from divine justice, there is only one way: the love taught by Jesus. "
Suggestions for reading:
Book of Spirits
Moral Laws Today, Author: Christiano Torch
The moral laws, by Rodolfo Calligaris