Officials have written to three supporters telling them they are banned because they "have displayed a desire to promote" their "dislike of Oldham Athletic."
Bradley Knowles, director of Oldham Athletic Supporters Foundation, was one of the fans to receive a letter demanding they stop attending matches.
Dominic Weiss and Nathan Price will also be refused entry to Boundary Park for the next three years.
Oldham Athletic’s General Manager Steven Brown wrote: “You have regularly displayed your desire to promote your dislike of Oldham Athletic Football Club, its management and its progression; and you are influencing others to do the same.
“You are taking deliberate steps to harm the club and cause distress.”
Other fans have criticised the club for taking this action and now the national supporters union has weighed in.
It said in a statement to ITV News: “It is always a grave concern when a football club bans its supporters not for breaking ground regulations but seemingly for doing no more the voicing discontent about how their clubs are run.
“We hope that OAFC takes note of the overwhelmingly negative reaction to these arbitrary bans and overturns them.
“In the meantime, The FSA will continue to afford advice and assistance to individual supporters and supporter organisations of Oldham Athletic.”
Oldham Athletic said the three banned supporters made "deliberate steps to harm the club."
A club spokesman said “After careful consideration we have taken the step of banning three supporters.
"We respect the right of any fan to protest and have not taken any action, to stop peaceful protest.
"These supporters have been banned as they have taken deliberate steps to harm the club and the people within it and have encouraged others to do so “