The popular card counting strategy is widely known as being unfair and illegal, but contrary to the common knowledge, it is actually perfectly legal.
“Card counting” in Blackjack is allowed and legal contrary to the common belief. This technique involves following carefully which cards have been dealt and which are still in the deck throughout the game. Films such as Rain Man and 21 show this technique as a form of magical ability, but it’s in fact nothing an ordinary person cannot do with a bit of training and use of arithmetic. However, this progressive approach to Blackjack hasn’t been banned in the casino world, but if the dealers notice that one is doing it, especially if they start winning big they might ask the player to leave. One vivid example is the famous Hollywood actor Ben Affleck, who has decent card counting skills and who was banned to play in a casino in 2014 because of it. Another approach to beating card counting on the side of casinos is to change the rules slightly or make use of a more frequent deck shuffling throughout the game.