Any legal challenge over the Carlos Tevez transfer saga would be futile, the Premier League has warned.
Tevez joined West Ham along with Javier Mascherano in August
The decision not to dock West Ham points over contract irregularities - and whether he should still be playing - has been questioned by other clubs.
But the Premier League confirmed to BBC Sport it had written to all 20 member clubs stating that any challenge would be "bound to fail".
Sheffield United, however, insist they will continue their fight.
A second Premier League letter, making it clear Tevez is free to play on, was also sent out.
It allows the Argentine striker to face Manchester United in the Hammers' last game of the season - a match West Ham may need a point from in order to stay up.
A draw, or a victory, would certainly see West Ham survive no matter what happens elsewhere.
Sheffield United revealed they have consulted their legal team and contacted the other three clubs with their observations - and have shrugged off the letters.
West Ham were fined £5.5m by an independent disciplinary commission on 27 April over their signings of Tevez and his compatriot Javier Mascherano.
The club was found guilty of acting improperly and withholding vital documentation over the duo's ownership.
Sheffield United plc chairman Kevin McCabe said: "It was an unjust penalty. We might as well all field illegal players every week. Here are West Ham still playing an international whose signing has breached the rules. It's just not on."
Tevez and Mascherano, who has since joined Liverpool, were part-owned by Media Sports Investment, the company formerly run by Iranian-born businessman Kia Joorabchian - contravening league rules over third-party ownership.
Sheffield United, Wigan, Charlton and Fulham joined forces last week to explore the possibility of contesting the commission's decision.
But The Times reports that the Premier League has told all 20 clubs that any challenge to the commission's findings "would fly in the face of the disciplinary structure that the clubs themselves created and we consider would, as a matter of law, be bound to fail".
The second letter also makes clear Tevez's current position and eligibility for West Ham after the club tore up the original third-party agreement with Joorabchian.
"The Premier League made it very clear to West Ham that unless it could be satisfied that all trace of any third-party ability to influence West Ham's policies or the performance of its team was removed, Tevez's registration would be terminated," said the letter.
"Assurances were received in a satisfactory form from West Ham. West Ham has assured us that it has terminated the contract.
"It has also indicated that under no circumstances will it regard the contract as binding on West Ham and that it will defend any proceedings brought against West Ham seeking its enforcement."
Mel Goldberg, a lawyer for Max Bitel Greene who specialises in sport, told BBC Sport that the clubs fighting the ruling were doomed to failure.
He said: "The clubs have agreed to accept the decision of the Premier League in these matters.
"Whether they like the decision or not, they are stuck with it.
"Everyone has to accept that West Ham will not be docked points and at the end of the season, the three clubs at the bottom of the table will go down."