Most casinos spread the word that to count cards in blackjack is illegal. The truth of the matter is that card counting is a perfectly legitimate strategy. No United States jurisdiction or statute prohibits gamblers from counting cards. However, most casinos still provide the game even if they know that skilled players can benefit from it.
The reason why casinos prohibit card counters from playing blackjack is because they do not want to lose money. Las Vegas casinos ban card counters from their halls because it is a private establishment and the owner has the prerogative to choose who they will permit to enter their premises.
Casinos have invested a lot of money and effort in trying to foil attempts to count cards in blackjack. Among the newest technologies used by casinos to combat card counting are surveillance cameras, computerized programs, scanners, multiple splitting, rule modification for splitting, doubling down, or multiple hands.
Some states, such as Nevada, are not allowed to implement these countermeasures. In New Jersey and some other states, casinos have the option to implement restrictions on the countermeasures against skilled gamblers.
However, these countermeasures likewise offer some disadvantages to the the casino. Shuflling the cards several times decreases the playing time of gamblers who are not counting cards and eventually it will decrease the winnings of the house. As a remedy for such problem, casinos now utilize automatede shuffling machines. A deck of carrds is simultaneously shuffled while another deck of cards is being used in play.
Some other models such as the Continuous Shuffle Machine lets the dealer return dealt cards to a shoe without interrupting play. These machines are perfect for eliminating whatever advantage gamblers can get from traditional card counting strategies. In online gambling, shuffling is done at the beginning of a new round which always gives the advantage to the casino.
In some instances, pitbosses who suspect that a player is counting cards approaches the player and invites them to play other games aside from blackjack or ban the counter from the casino. In states where banning players is not allowed, pitbosses requires the players to make a flat wager and prohibits them from joining the game in the middle of the shoe. This is an effective strategy in eliminating whatever advantage the gambler will have from playing multiple decks.
Another countermeasure that casinos implement against players who count cards in blackjack is to share the name and picture of the player with other casinos.
In the end, casinos will still be the winners in all of these as they always end up earning more profit than their patrons.