Moral justification for the execution of criminals of war?

[Angrboda]

A lot of people, including people who are serving a life sentence, disagree with you.
A lot of people who found a meaningful life behind bars demonstrate you being wrong with this generalisation.
Of course your life would be meaningful behind bars, maybe under any circumstance, i dont deny that.

I have apparently failed to make my point clear.

My earlier point was that from a pragmatic perspective, execution should save money and totally eliminate the chance of re-offense-- but that point was refuted on the basis that the execution process (in the US at least) is exceedingly expensive.

But I don't think that should be the case.  If execution merits appeals, lots of expensive legal work, and so on, SO DOES a life sentence, because the loss of quality of life is so drastic.  When I say that a life sentence is the end of a meaningful human existence, I base that on the loss of agency involved in imprisonment, and on the loss of the pleasures that a free person may enjoy, especially in the US.  Yes, some can to some degree make lemonade out of their lemons, but I suppose they would much rather be outside, where they can exercise free will and intent.

The difference is that a life sentence represents reversible error, whereas execution involves irreversible error. Decisions regarding irreversible error demand more resources, due to the irreversibility of getting it wrong.