Kimberley Jonathan was elected last October but candidate Sheldon Wuttunee challenged the result.
The appeal tribunal overturned the result on Wednesday and a new election for vice-chief will now have to be held.
FSIN Chief Perry Bellegarde says in a release the executive, member First Nations, elders and senate fully accept the appeal tribunal ruling.
Under FSIN rules, if an election is overturned and there is more than 18 months remaining in the term, a byelection must be called.
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