In a word, no. Card counting is not illegal.
You cannot use any devices to work with you in card counting. Pocket sized computers and other gadgets which they can display as card counting aides are illegal. If you are ok casino caught using such a device you will be caught in Las vegas. A card counter can only use his or her own mind to card cards.
A casino will be on guard for card display. They watch for players who play in a business like manner. They look for players who don’t interact with the dealer or other people. They look for players using basic strategy. Casinos will count along with a suspect card counter. A player will be defined as a counter when the casino sees little leaguer raise his bet when the count is in his favor.
Team play was big in the 1990s. A team would consist of several players at a table gambling on only the table minimum and counting cards. Since these players never increased their can guess, the casinos could not spot them as display. These players then signal another, “big money” player. The “big money” player wanders from table only stopping where the count is in his favor and only gambling on large amounts. Without the typical can guess increases of a single card counter, teams of players were difficult for the casino to spot.
A casino may escort you off areas, read you the riot act, and threaten you with trespassing should you return. They may share your picture and profile with other casinos. However, this is not likely should you not are wagering large chunks of money.
A card counter who is counting inadequately or who is losing may just be allowed to play. A casino is happy to have anyone lose at any of their games. A card counter who is winning will often provoke some action by the casino. The easiest thing for the casino to do is instruct the dealer to shuffle with greater frequency, perhaps every third or 6th hand. This makes the counter constant reset his count and he will never see the positive count he needs.
In order to prevent being seen as a card counter, a player can do unique. First, little leaguer should act in a relaxed manner. Second, it may be prudent to break basic strategy. For example, you could split tens every once in a while. A casino is likely to label that you a recreational player if you break basic strategy from time to time. Finally, a player can be careful together with can guess. A five to ten times increase in the can guess may just be ignored. Beyond ten times increase will draw scrutiny. Also, some players recommend changing your can guess in proportion to the running count. Thus the can guess is always changing and it’s hard to notice increases.