For those of you who still think Wynne's case is covered by Article 6 read this
It's mainly about eligibility concerning Northern Ireland and the Republic of Ireland (Several people born in N.Ireland are entitled to both a British AND an Irish passport from birth). The important part as far as Wynne's situation is concerned is about a quarter of the way through the article: The IFA (N.Ireland) went to the CAS to dispute the meaning of Article 6 and this is their findings:
The CAS, going into great detail in order to clear up the IFA’s misconception, stated:
“Whether the player’s multiple eligibilities are based on one single nationality and/or on two or more nationalities is disputed. The IFA submits that Article 16 is applicable to any player who is entitled to play for several associations on the basis of multiple nationalities whereas the FAI submits that it is only applicable to a player who is entitled to play for several associations on the basis of a “shared nationality”, i.e. a single nationality that entitles him to represent two or more associations.
Based on the historical interpretation, it appears that the current Article 16 implements Annexe 2 of the Regulations for the Status and Transfer of Players (edition 2005). Both provisions have a quasi-identical wording. The title of Annexe 2 (“Eligibility to play for association teams for players whose nationality entitles them to represent more than one association”) as well as the FIFA Commentary compel the conclusion that Article 16 covers exclusively the situations of players with “shared nationality”.
The fact that Article 16 applies only to players with “shared nationality” is also confirmed by its wording as well as by the systematic interpretation:
So it's obvious that Article 6 is explicitly referring to someone who has a single nationality that entitles them to play for more than one association, and if NZF end up taking their appeal to the CAS it's going to end in failure as the CAS have already ruled on this very situation.
Note: Article 15, 16, 17 & 18 have more recently been renumbered 5,6,7 & 8.