Derek Kelly, 46, argued poker is a game of skill so he did not need a licence under the 1968 Gaming Act, as the law requires it only for games of chance.
But the jury at Snaresbrook Crown Court disagreed and took less than two hours to find him guilty of organising games at his Gutshot Club in central London.
The prosecution said the Irish man took a cut from the prize pot as well as charging the players for participating.
Kelly, a financial analyst from Greystones, Co Wicklow, Ireland, was found guilty of two counts of contravening of the Act.
The charges related to games of poker, organised on 7 December 2004 and 27 January 2005, at the private members club in Clerkenwell in which a levy was charged on the winnings.
The Act states a licence is needed to host games of chance such as blackjack and roulette - but not games of skill, like chess and quiz machines.
The trial centred around the popular Texas Hold 'Em variant of poker, in which each player is dealt two cards and then a "community pool" of five cards is placed on the table.
The jury was asked to decide whether it was a game of skill or chance, or a combination of both.
Graham Trembath QC, told the jury that they alone would decide the verdicts.
Shuffled cards
He said: "Is poker a game of mixed skill and chance? That is for you to decide. The prosecution submit that common sense dictates that it is.
"Why do we say that? We say that because before a game can start someone shuffles the cards."
Zeeshan Dhar, defending Kelly, told the jury poker required such a level of skill it did not fall within the remit of the Act.
He said: "If we accept that a game of chance includes all games of combined chance and skill every game you could possibly think of would fall foul of this particular Act."
A date for sentencing and consideration of costs has been set for 16 February.
The judge has said: "I do not consider this to be a case where any sentence of imprisonment is appropriate."
The prosecution's legal costs were £16,000 with a bill of £6,800 for investigation of the case.
Serious breach
He said he was "minded" to make a very substantial" cost order against Mr Kelly with a relatively "modest" penalty.
In a statement issued after the trial the Gambling Commission said it was pleased to see the case had concluded.
"The law has always been clear, commercial gambling needs to be properly regulated to ensure that members of the public are protected from exploitation.
"The Gutshot was not regulated and was in serious breach of the Gaming Act 1968," the statement read.
Mr Kelly, a married father of four, is chairman of the Gutshot private members club, which opened in 2004. The case brought some excellent points to light but questions still seem unanswered in my eyes, Mr Kelly did break the law by taking fees from prize pools and taking a rake from cash tables, to the best of my knowledge he was told that he could continue once he made changes to these matters, Mr Kelly decided not to do so and was therefore prosectuted. Mr Kelly is a business man and he made that point that poker tables and equpment don't fall from the sky, this is very true and every business must make money to sucseed, the poker room needed to beable to cover the costs which i am sure were high for a place like the gutshot with highly qualified trained delaers, supervisors, equipment and so on. All in all a sad week for poker and i feel for Mr Kelly and the members of the Gut Shot, is there a appeal on the way? I Hope So! Derek Kelly's argument that poker is a game of skill and not one which is left to chance has sparked much debate among the gaming community. Read more from the bbc's report...CLICK HERE
Let us know your opinion: info@cockneypoker.com Report from: BBC NEWS