Generally, D&D seems to follow the line of thinking that absolutes of Good and Evil can and do exist, so I guess it's possible to have a LG character anywhere, even if their own society considers them evil or lawless. So I have to concede on that.
I was tempted to say that history is so tightly restricted on Athas that nobody could be nostalgic about the better times, but I think the PHB and Campaign Setting make special concessions for that very thing. (Notably, PCs are always assumed to be literate even though most of Athas isn't.) So I have to admit that your so-called Nostalgic Hero can and would exist in Athas.
Plus, if a character belongs to a tribe, I guess they could be Lawful Good with respect to that tribe, even if that tribe's ideas on justice are far different from Pelor's. But again, I don't think D&D addresses such issues. Though I'm sure nerds will post in forums on the subject at great length.
Yes I know it's ironic, shut up.