The message from Eteläpääty came on Tuesday, a day after Russian President Vladimir Putin recognized the breakaway regions of Donetsk and Luhansk in eastern Ukraine.
The Joker has not played a KHL match since January 11, when the league chose to cancel the rest of the regular season and instead start the playoffs after the Beijing Olympics.
There, Jokerit will meet Spartak Moscow in a week, on March 1.
The supporters' association now wants Jokerit, who is in his eighth season in the KHL, to withdraw from the league with immediate effect.
"If the Joker continues to play, it will result in excessive damage that may never be corrected," the open letter states.
Roope Räty, vice chairman of Eteläpääty, says that the association will not follow any possible play-off matches.
- It is of course up to each individual to decide what to do: do you go to the matches or do you participate in the protests.
As an association, we are not involved.
We do not go to the matches and do not support Jokerit in the KHL, he says to Yle Urheilu.
CLIP: Finland historical champion - took Olympic gold after thriller (February 20)
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Finland celebrates historic Olympic gold.
Photo: TT