Essentially yes. It's made abundantly clear in the novels and DFRPG that specifically taking a life through the use of mortal magic is a violation of the natural order of the universe, on par with altering a person's mind, raising the dead, or altering the past.
This isn't a moral judgement in any way, and Anastacia Lucco points this out bluntly to Harry. The Wardens do not uphold morality, they uphold the Laws of Magic.
And yes, you're right, sometimes it means a character can be punished for doing what they believe to be the right thing. Like Harry killing DuMorne. That was in self-defence, and still was a violation of the Laws of Magic, setting up Harry's initial conflict with the Council. This is also why, as stated in the novels, the Wardens carry swords, so they can finish off an opponent, or carry out an execution, without using magic.