Casinos will use continuous shufflers which kill counting 100% or will cut off multiple decks at the end of the shoe so one cannot get a very positive count and more certainty that the deck is in their favor. In addition, as stated earlier, the type of counting these people did in the early days which was most lucrative is easily spotted. So now modern counters have to apply "camouflage" which includes placing higher bets when the deck is not in their favor to make it appear they are betting randomly, and also reducing their bet spreads. All of these eat into the theoretical return, and make it much less lucrative if not entirely not worth it. So modern advantage players look for casinos that don't watch as carefully or dealers that are not cutting off enough cards.
They don't to justify anything. Casino bans are not subject to judicial review.
[1]http://m.startribune.com/gambling-problem-states-let-you-ban...
Huge fines, potentially followed by loss of license.
You do not want to go there. With the elevated scrutiny on gambling operators (triggered in part by the US opening up, in part by the increased competition, and in part by the receding margins) all the regulators are itching to make examples out of suitable villains.
Disclosure: I work for a [UK] gambling company and deal with compliance matters on an almost daily basis.
An interesting question to be honest. I'd somehow expect any prosecution to be far too complex for the parties to enjoy court.
Sure, you excluded yourself but then went to the casino after all. Did you do that because addiction caused you to misjudge the risks? Did you go there with the intention of defrauding the casino when you lost money? (Gambling establishments that fail to prevent self-excluded customers will have to refund their losses. And if they do that only after regulators get involved, there will be fines on top.)
Proving the nature of intent for that kind of violation could be very messy indeed.
There's an interesting article on how security detect card counting[0]. My take is that it's not a science, instead the security/ pit boss' who spend significant time watching players would develop a 'feeling'.
[0] https://www.huffpost.com/entry/how-casinos-know-that-you_b_6...?