It has been discussed five billion times or more (okay, hyperbole, but it gets discussed a lot). There is no consensus of any sort. Some people (including myself) believe you'd still get Lawbreaker, while others think you don't. No clear answer has been determined.
This thread will rapidly become another such argument, but that's the heart of things. It's really up to you, the GM.
Though...I am a bit curious why a Holy Warrior would need an answer to that question. I mean, is he killing human beings with magic? Because that's really the only Lawbreaking I can think of that any sort of Holy Warrior should even be contemplating and even there, well, I'd just get a sword or axe and use that instead.