A ruling is to be given by the Court of Appeal on the issue of what is cheating.
In 2014, top poker player Phil Ivey lost his High Court case against the owners of London's Crockfords Club over £7.7 million won from playing a version of baccarat known as Punto Banco at the Mayfair casino two years earlier.
Mr Ivey, 39, who lives in Las Vegas, was told the money would be wired to him and he left for home, but it never arrived, although his stake money of £1 million was returned.
Genting Casinos UK, which owns more than 40 casinos in the UK, said the technique of ''edge-sorting'' used by Mr Ivey - which aims to provide the customer with an element of ''first card advantage'' - was not a legitimate strategy and that the casino had no liability to him.
It claimed that Mr Ivey's conduct defeated the essential premise of the game of baccarat so there was no gaming contract - or constituted cheating.
On Thursday in London, three appeal judges will give their decision on the new challenge brought by Mr Ivey.
In the High Court, Mr Justice Mitting said the fact that Mr Ivey was genuinely convinced he did not cheat and the practice commanded considerable support from others was not determinative of whether it amounted to cheating.
Mr Ivey had gained himself an advantage and did so by using a croupier as his innocent agent or tool, he said.
In the judge's view, this was "cheating for the purpose of civil law".
Mr Ivey responded that he did nothing more than exploit Crockfords' failures to take proper steps to protect themselves against a player of his ability.
''I was upset as I had played an honest game and won fairly. My integrity is infinitely more important to me than a big win."
At the appeal, Mr Ivey's counsel, Richard Spearman QC, said the judges had to decide what cheating involved or whether Mr Ivey's conduct amounted to cheating.
"The real question is - what are the constituent elements of cheating?"
In its ordinary meaning, he said, cheating involved dishonesty and there was no difference between the criminal or the civil law in that respect.
He argued that Mr Justice Mitting had decided that Mr Ivey had not conducted himself dishonestly and there was no deception of the casino in what took place.
As Genting said that cheating involved not just dishonesty but behaving unfairly, the court would also have to grapple with what was unfair in the "cat and mouse" environment of a casino.