The Premier League's rules on commercial deals from 2021 to 2024 were declared "void and unenforceable" by a tribunal after a challenge by Manchester City.
Premier League champions City sued the organisation over its associated party transaction (APT) rules last year with a panel declaring three aspects of them unlawful in October.
The APT rules seek to ensure deals done between clubs and entities linked to their owners are for fair market value.
The Premier League said the October ruling required only discrete elements of the APT rules to be amended, which clubs duly voted to do a month later.
City's position in October was that the whole set of rules was void and that no changes should be made. Both sides sought clarification of the ruling from the original panel.
The tribunal's conclusion was reported by British media, including the BBC. It read: "In the first partial final award it was declared that the APT rules and amended APT rules were unlawful in three respects.
"There now arises for decision the question whether those three respects can be severed from the remaining APT rules so that those remaining APT rules are valid and enforceable.
"The three respects in which the APT rules and amended APT rules were unlawful cannot be severed with the result that the APT rules as a whole are void and unenforceable."
Manchester City have now also separately challenged November's amended rules, which is being heard by the same arbitration panel.
On that, the panel said: "However, there remains for decision (in the fresh arbitration commenced on January 2025) whether the November 2024 amended APT rules are valid and effective."
The decision is crucial for how commercial deals are governed in the future.
The Premier League said in a statement: "The tribunal's decision has found that the three narrow aspects of the old APT rules, previously found to be unlawful, cannot be separated from the rest of the previous rules as a matter of law. The result, the tribunal has determined, is that the previous APT rules, as a whole, are unenforceable.
"However, the previous APT rules are no longer in place, as clubs voted new APT rules into force in November 2024. This decision expressly does not impact the valid operation of the new rules.
"The league continues to believe that the new APT rules are valid and enforceable and is pressing for an expeditious resolution of this matter."
Uncertainty around the APT challenge was understood to be a factor in Premier League clubs deciding not to adopt new financial rules at a meeting on Thursday.
Instead, clubs will be governed by the existing profitability and sustainability rules (PSR) next season.
