Short Version:
Vernon (Stuart Townsend) and Dean "The Dean" Stevens (Sylvester Stallone) were actually pulling a con together to steal a lot of money from Vernon's former grifter partners.

Long Version:
A star-studded con movie worth seeing.  After conning Larry Jennings (Jamie Foxx) out of money that actually belonged to Mob boss Max Malini (Patrick Bauchau), former partners with an unresolved past, Vernon, Charlie (Gabriel Byrne), and Tiffany (Thandie Newton) are buying their way, for $250,000, into an illegal high stakes poker game where they hope to win against a legendary cardsharp, Dean "The Dean" Stevens.  After dodging Malini's hitmen, Vernon finds himself at the poker table with the legend himself...and Max Malini (who has no idea that these are the con men who took his money).  The game goes on for a while and Vernon and The Dean seem to be the clear leaders of the game.  Several opponents are eliminated (among them, Star Trek's Michael "Worf" Dorn) and it comes down to a heads up match between Vernon and The Dean.  During a quick break, Vernon, Charlie, and Tiffany discover that The Dean is using marked cards to read his opponents.  They decide to set a trap for him using Vernon's card manipulation skills.

The final game is five card stud with The Dean being dealt a king in the hole and showing a king and two queens on top.  Vernon has a 7 hole card with two jacks showing, but Vernon has palmed a jack and is preparing to use it.  After some by-play and betting, it comes down to all the money in the game on the line, plus an extra fifty thousand provided at the last minute by Charlie and Tiffany to back Vernon.  Before the cards can be turned, however, Malini's hitmen come into the room and recognize Charlie and Vernon.  Guns are drawn and it looks to be a tense situation until The Dean intervenes and says he wants to see the Vernon's hole card first.  Vernon smirks and uses a sleight of hand maneuver to switch his original hole card for the jack when turning it over.  He shows trip jacks.  The Dean looks defeated and turns to his girlfriend (Melanie Griffith) and says in a tired voice, "I always knew this day would come."  He turns back to Vernon and his face transforms into a smirk, "Just not today."  He turns over his hole card and shows a queen, for trip queens, having somehow switched out his king with nobody the wiser.  Vernon looks shocked because he stacked the deck and knew what The Dean should have had in the hole.  Charlie, Tiffany, and Vernon can only look horrified as they realize all of the money that they have just lost.  Malini, in a magnanimous gesture, forgives them and tells them to get out of town.  Charlie and Tiffany leave Vernon in disgust and go off on their own.

Sitting in a café by himself, Vernon is suddenly confronted by The Dean, who drops a satchel full of money in front of him.  It was all a setup from the start between Vernon and The Dean to pull a con on Charlie and Tiffany.

Thanks Bruns!