I'm assuming he means one of the two cards that are referenced by the "2-Casinos" action card section, but not mentioned elsewhere in the rulebook.
Las Vegas Boulevard rulebook wrote:
However, if another player in the same turn plays the ...
... “Skip” card, that player is not affected by the “2-Casinos” card.
... “Turn-Dice” card, then this player may intentionally place the additional dice on the first casino again (and therefore does not need to place dice on a second casino).
... “Double-Trouble” card, this player is not allowed to place dice on the first casino and then flip the 2 additional dice (for a double) to the number of the same casino!
Edit: I'd like to know the answer to his question as well.