A group of Charlton fans have taken up occupation in the boardroom at The Valley in protest against EFL rules on club ownership.
The League One club is at the centre of a legal battle between rival parties that want control.
Despite failing the EFL's Owners' and Directors' Test, prospective new owner Paul Elliott is seeking a court injunction to try to prevent the sale of the club to a rival bid being led by US-Danish businessman Thomas Sandgaard.
Charlton were bought by East Street Investments from Roland Duchatelet for £1 in January, and fans on Saturday gathered at The Valley to protest against the rules which allow that to happen.
With conflicting parties claiming ownership of Charlton, the fans group that has occupied the boardroom is vowing not to leave until the legal owners of the club formally request in person that they vacate the premises.
An estimated 500 supporters gathered outside the League One club's home ground at around midday on Saturday and a smaller group was seen singing in the boardroom, displaying a notice on the window reading: "Our pound is bigger and better than yours, #ESIOUT".
In the peaceful protest, some Addicks fans displayed £1 coins, in reference to Duchatelet's sale of the club earlier this year.
The group Fans4Fans issued a statement to say some Charlton supporters "will not be leaving [the boardroom] until the current owners of Charlton Athletic Football Club formally request, in person, that we vacate the premises with immediate effect.
"We also request an extensive update on why Paul Elliott has been able to formally lodge an injunction preventing the sale of Charlton Athletic Football Club and when this case is to be heard.
"In addition, how can a man who has failed the owners and directors test, appeal the sale of a business he will not be able to sufficiently control or finance?
"If this direct action does not bring about change for football clubs then we are left with no choice to attend the English Football League Headquarters and its sponsors offices and in turn take direct action against them."
The statement added: "The actions you have witnessed today are a direct consequence of the failings of the governing bodies that represent all football clubs throughout the English football pyramid.
"It has become apparent that the current processes and systems in place, deemed acceptable to the governing bodies, are far from acceptable with a large majority of football fans.
"Football fans will no longer stand impassively and allow their beloved clubs to face uncertainties such as administration and potential expulsion from their league.
"What you have seen take place already with the occupation of IPS LAW offices in Manchester was the beginning of direct action to force change with the EFL.
"The flaws in the Owners and Directors Test {OADT} are visible and we require immediate change in this. We are suggesting that: No Football club should be sold for £1, Funds should be proven and placed into an EFL club allocated account prior to completion of the purchase of a football club
"A minimum cover of costings that is decided by the EFL. Based on a club by club scenario. This should be held in an account for a period of 24 months to enable that club to run sufficiently for an extended period.
"This will be managed by the clubs but audited by the EFL quarterly, to ensure that the funds held in the club account are for the day to day operations of running the football club.
"Then the OADT should then be undertaken not the other way around."
Sky Sports News has contacted the EFL for comment regarding accusations surrounding the League's Owners' and Directors' Test.
Meanwhile, US-based businessman Sandgaard has told Sky Sports News that he expects to reach an agreement in principle to buy the club by the end of this week.
"It might be realistic, that we can have an agreement in place in principle this week," he said, "that's what I am hoping.
"Maybe we should expect a few minor surprises right before the finish line so (the whole deal may take) a few more weeks but I hope we have an understanding this week."
Lee Bowyer's side were relegated to League One in 2019/20, spending just one campaign in the second-tier after a three-year absence.