The Premier League's decision not to dock West Ham points after the club breached regulations in the signing of Carlos Tevez and Javier Mascherano prompted surprise and anger from their relegation rivals.
Tevez's goal at Manchester United safeguarded the Hammers' Premiership status on the final day of the season, but relegated Sheffield United have threatened legal action over the Premier League's ruling.
BBC Sport looks at the ins and outs of a complicated case and how likely any appeal against the decision would be to succeed.
WHAT EXACTLY DID WEST HAM DO WRONG?
It is not explicitly against Premier League rules for a club to sign a player whose economic rights are owned by a third party - as in the case of Tevez and Mascherano.
Tevez (left) and Mascherano joined West Ham in August
However, rule U18 states: "No club shall enter into a contract which enables any other party to that contract to acquire the ability materially to influence its policies or the performance of its team."
When signing Tevez and Mascherano, West Ham entered into a private agreement with the companies which owned their economic rights.
The contract stated, among other things, that those companies had the right to terminate the players' contracts upon payment to West Ham of £2m (in Tevez's case) or £150,000 (for Mascherano) in any transfer window.
By entering into that agreement, West Ham clearly broke rule U18.
Premier League rule B13 states: "In all matters and transactions relating to the league, each club shall behave towards each other club and the league with the utmost good faith."
When Tevez and Mascherano were registered as players, West Ham failed to disclose that they had entered into an agreement with third-party companies.
In my opinion, West Ham received favourable treatment
In its judgement, the Premier League's independent commission said: "This was not only an obvious and deliberate breach of the rules, but a grave breach of trust as to the Premier League and its constituent members.
"In our finding the club has been responsible for dishonesty and deceit."
West Ham pleaded guilty to both breaches of Premier League rules.
WAS CARLOS TEVEZ ELIGIBLE AFTER THE RULING?
There was never a problem with Carlos Tevez's, or indeed Javier Mascherano's, registration as a player.
West Ham's mistake was in not disclosing to the Premier League that they had entered into an agreement with the companies that own the pair's economic rights.
Tevez scored some crucial goals as West Ham escaped the drop
In its conclusion, the commission said: "We order the registration of Carlos Tevez can be terminated by the Premier League."
However, West Ham immediately ripped up the agreement they had with the third-party company and the Premier League has since said it is satisfied the club "acted in a manner that is consistent with them having terminated the offensive third-party agreement".
Wigan and Sheffield United argue that for a contract to be properly terminated, all parties involved must agree.
Kia Joorabchian, who owns one of the third-party companies and was influential in Tevez and Mascherano's arrival at West Ham, has told the Daily Mail newspaper West Ham "unilaterally terminated the agreement and I have left it in the hands of my lawyer".
However, BBC Sport understands that the Premier League can only ask for evidence that the club has terminated the agreement as the third-party company does not fall under its jurisdiction.
The only possible action that can come of West Ham's termination of the agreement is that Joorabchian could consider proceedings against the club.
WHY CAN MASCHERANO PLAY FOR LIVERPOOL?
West Ham's mistake was not in entering into an agreement with a third party - but in the detail of the agreement and in their failure to disclose it to the Premier League.
Mel Goldberg, a lawyer for Max Bitel Greene who specialises in sport, explains: "Mascherano subsequently signed for Liverpool pursuant to a contract entirely different in form to that agreed by West Ham and which has been approved by the Premier League."
WHY WEREN'T WEST HAM DOCKED POINTS?
The commission concluded that a deduction of points "would normally follow from such a breach of rules".
However, it went on to say that docking points would "not be proportionate". It gave seven reasons for that decision, including the club's guilty plea, and also:
A points deduction so late in the season might have consigned the club to relegation
The players and fans of West Ham are in no way to blame for the situation and therefore should not suffer
Goldberg admits he found those reasons for the penalty baffling from a legal standpoint.
"They could have been harder on West Ham," he told BBC Sport.
"In law, the fans have no bearing on the case. It's no good saying 'we don't want to upset the fans'. What about the Wigan fans? The timing of the case being presented is also irrelevant.
"The Commission shot themselves in the foot. It comes down to whether the rules have been broken or not and they should have been penalised appropriately.
"In my opinion, there is no question about it. West Ham received favourable treatment."
COULD OTHER CLUBS SUE THE PREMIER LEAGUE?
On Friday 4 May, West Ham's relegation rivals Charlton, Fulham, Sheffield United and Wigan sent a letter to the Premier League warning that they were considering what steps to take in regards to the Independent Commission's judgement.
Sheffield United went down - prompting boss Neil Warnock to leave
In response, the Premier League sent a letter to all 20 Premiership clubs telling them that any legal action would be "bound to fail".
Goldberg agrees. He told BBC Sport: "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 the three clubs at the bottom of the table at the end of the season will go down."
Sheffield United, who were relegated on the last day of the season, maintain that they want a new disciplinary hearing and if one is not forthcoming, they will pursue legal action.
COULD OTHER CLUBS SUE WEST HAM?
Another option open to any or all of the other 19 Premier League clubs could be to take legal action against West Ham for deliberately breaking Premier League rules.
Goldberg says: "I do think that it is a possibility. It could be a costly move - but not necessarily - and they could argue that West Ham have not acted in good faith."