It was mentioned earlier in the story (chapter 21) during the MC's flashback, but pretty much it's considered taboo and 'against nature.' You are to 'never restore a living organism' because of the moral/ethical issues but mainly because it's impossible to predict the result/form it will take when restored. The MC knew this but tried to 'save/restore' his friends anyway because he had a mental breakdown after watching them get slaughtered (he realized after the impact of his decision but because of his power couldn't fix it). I'm curious how they will try to convict him though because all of his friends should be dead dead now (he had 6 undead friends and the deal was to use the ML's power 1 for each friend plus an extra use (especially one for each dungeon- 7 total)).
Addressing the outrage, if we are being honest, this world is hella unempathetic and hypocritical because they originally criticized the MC for retiring earlier in the story, despite the fact that kid had all of his friends slaughtered in front of him. Then they critiqued him for being the 'weak link' and causing issues and then they praised him and put him on a pedestal.
Ironically the only one who has put any thought into and has been considerate of the MC's situation and mental state is the ML and his main goal was to improve the MC's condition as a means to benefit himself
lolll nevermind, I just looked again and for some reason, they haven't killed off the last friend yet (chapter 72- honestly the ML probably has put it off to blackmail the MC some more). But maybe he has a different plan, in place?
but is turning your friend into zombie a crime tho? they were already dead I dont understand why everyone is so shock and outrage when dungeon/magic/monster exist in their world?