"In sociology and social psychology, an in-group is a social group to which a person psychologically identifies as being a member. By contrast, an out-group is a social group with which an individual does not identify."
Implying it is about psychological identification. This makes sense for groups like libertarians, socialists, rationalists and political ideologies or cultural leanings where individual choice and agency matters, perhaps more than for "immutable" characteristics bestowed upon people by birth. Even so, there is fuzziness (e.g. what if you call yourself one, but most people who call themselves one don't recognize you as one?).
But there are usages where it's unclear if ingroup and outgroup are about self-identification or categorization by others, or even some "objective standard" (all people with trait X are part of an ingroup and you can't join if you lack X). I don't think everyone uses the Wikipedia definition based on "psychological self-identification" when they speak of the terms. I have heard the term used for situations where the person is ascribed to a group and other members of the group are called the person's "ingroup" without knowing anything about psychological state of self-identification. Is this a misuse of the term?
Imagine a person that dislikes the country they are born in and never left -- they reject the label of (insert demonym of nation) to describe themselves -- perhaps they aspire to be another country's citizen (but can't accomplish that for practical reasons) or maybe even dislike the idea of nationalism or patriotism and identify as "citizen of the world". They do not favor their own country and support other countries economically or even politically.
Would this person be considered (1) disloyal member of ingroup by fellow members of the ingroup or perhaps outgroup sympathizer (2) outgroup member by fellow citizens?
How does the ingroup/outgroup distinction handle situations where the individual and other members of a group disagree on whether they are members of the same group?
Or does the ingroup/outgroup distinction only apply where self-identification and broader consensus agree on what group a person belongs to, which becomes the person's ingroup?