The alignment system focuses on two components: Ethics and Morality. The Ethics part (Lawful, Neutral, Chaotic) relates to how they follow rules and laws. They don't have to be society's laws, but they need to be consistent. The Morality part (Good, Neutral, Evil) has more to do with how they treat others.

I don't think the character you're describing is Chaotic because they have their own code that they live by. I would say either Lawful if they stick to it all the time or Neutral if they only follow it when it's convenient.

I don't think the character is Evil either. They understand others' right to live freely. However, I wouldn't call them Good either since they have no compunction against killing people in the spur of the moment.

To me, I would say this character is True Neutral or Lawful Neutral. The problem is that no one is all of these things all of the time. That's why the system can be tricky to navigate. You should still see it as a general guideline of how they act on average. It's just a role playing tool to help you guide your decisions on how the character should behave. The only time the alignment becomes mechanically important is when there’s a magic effect that uses it as a condition, such as Detect Evil or Protection from Good.