Why cant a LG character live in any other alignment society?
If you can only be lawful with respect to society and you can only be good in respect to society, then we run into problems nearly immediately.
Because can you be Lawful Good in Prince John's England, where the lawful thing is to follow a potential usurper who is taxing the commonfolk to death and the Good thing is to break the law?
Let us take a tyranical state where "the trains run on time" and the people aren't too oppressed. Like Doctor Doom and Latveria. Can you be lawful good in that society, if you can only define law and good based on the society around you? After all, the tax money of Latveria is (partially) going to fund a supervillain who wants to take over the world, but who is also the rightful king of the country whom the people love (and they do love him, canonically, its what makes him an interesting villain)
And this was the point I was getting too, if you can only define Lawful and Good in the context of if you are following ideals of the society around you, than any country that isn't Lawful and Good is going to cause friction because the Good thing might be to break the law.
And, most examples people would likely be giving me involve some outside code or similar to be the source of the "Law"
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Because someone can view the world as a clockwork mechanism that follows a set of rules without agreeing that the laws of the land aligns with those rules. They follow a code, perhaps one handed down or even simply one that they read about.
They follow a set of rules because following those rules comes naturally to them. If they follow the ancient order of Herbacians, the Grand High Basil deserves his respect. The pirate king? Not so much, although they are far more likely to view someone with a title favorably than someone that is chaotic.
There's no conflict. Someone that is lawful will likely try to follow the laws of the land, as long as those laws don't force them to break their own personal code of honor.
So a person who believe the world works like a kingdom with the Gods acting as a Congress can't be Lawful?
And a personal code prevents you from being Chaotic? So, if I had a code that was something like "Never eat Fish on Friday. Never resheath your sword without killing someone. Always bow when you walk past a church. Always pay back insult with injury." Then they would be a Lawful individual?