Casinos don’t like card counters. Of course, the act of card counting in blackjack isn’t illegal. As long as you are keeping track of the current count, you won’t break any laws.
But if you use a device such as a small computer or an iPhone, you will find yourself in trouble.
Casinos don’t make it easy for card counting to take place. This is because they can kick anyone out without giving them any reason. If it suspects you of card counting, they can tell you to never come back.
In Atlantic City, casino don’t send patrons away on suspicion of card counting. Still, they use other methods to disrupt any attempt to either. The dealer will shuffle the deck after each hand. Someone will interrupt you as a distraction. They can also come up with some legal reason to get you off the property.
So, card counting isn’t illegal but it’s best not to get caught. The ability to do this involves keeping a low profile.
For that matter, card counting doesn’t need you to be a genius. What you do need to be careful of is not drawing attention to yourself. Especially when increasing your bets if you find an opportunity to do so.
Casinos tend to pass around information about advantage players. So, if they send you off one property, other properties will too.
That said, the laws vary from state to state about what you can do with card counting at casinos. Consult a lawyer if you do this anywhere else apart from Vegas and Atlantic City.