An enforced order for self-exclusion from a casino can be very effective at bolstering the willpower to refrain from gambling. The effectiveness comes from two features of self-exclusion, physical inaccessibility and reward diminution. Physical inaccessibility arises because the casino tries to keep you out, and in many jurisdictions can charge you with trespassing if you show up on their property. Reward diminution arises, in part, because the casino can confiscate any large jackpots that you might win, if you successfully sneak back in.
The legal basis for casinos to take away an excluded gambler's winnings, however, is not completely settled. (The casinos generally can't keep the confiscated winnings; rather, they are donated to a charity, perhaps one involved with fighting pathological gambling.) In Iowa, the state Supreme Court recently overturned a lower court ruling, deciding that a casino was within its rights to refuse to hand over winnings of over $9,000 to an excluded gambler. This particular gambler, however, was not self-excluded: he had been permanently barred from the casino following a conviction for criminal mischief arising from an incident where he attacked a slot machine.
The casino in question was in the news again last week, with exclusion again featuring as part of the story. The allegation is that a man made a bomb threat against the casino after he was refused admission because he did not show a picture ID. A requirement that casino patrons present IDs, incidentally, is very helpful in enforcing exclusion bans. Another helpful feature is US federal tax law, that requires withholding and form-filling before slot machine winnings of $1,200 or more can be paid. It was the necessity to fill out the tax paperwork that led to the excluded gambler's identification in the incident that the Iowa Supreme Court recently ruled upon.