Too drunk to lose $500,000 in Vegas? Lawsuit may not be such a long shot.

Is there such a thing as being too drunk to gamble – legally, that is?

Mark Johnston, a California businessman, says in a lawsuit that the Downtown Grand Las Vegas Hotel and Casino served him up some 20 free highballs as part of a shakedown tactic – to fleece him while he was drunk.

On a Super Bowl night he says he can’t remember, Mr. Johnston, who describes himself as a bit of a high roller, lost a whopping $500,000 – mostly on blackjack – including $250,000 that was credit extended to him during his binge.

"I mean, picture this: You're walking down the street – you're drunk, you're drunk – and somebody leans over and reaches in your pocket and steals your wallet. Do you think that's right?" Mr. Johnston said on CBS News, suggesting that’s what the Grand did to him.

In a city awash in nightly libation and keen-eyed gamblers, it’s going to be a tough case to prove, especially considered against the backdrop of a broader national debate about personal responsibility. Only this week, a New Jersey judge issued a ruling against an 18-year-old high school senior suing her parents for financial support after she moved out of the house.

Cultural sensitivities around personal responsibility also cropped up in a recent juvenile case in Texas, where a judge was criticized for ignoring prosecutors’ pleas for prison time and instead sending a wealthy 16-year-old to a tony treatment facility in California after he pleaded guilty to killing four people in a drunk-driving crash last summer.

But Johnston’s drunk gambler lawsuit may not be a total crap shoot, legal experts say. In fact, he might have a chance to win, depending on what surveillance video looks like  and given precedents where casinos have quietly agreed to settlement deals instead of going to a jury.

“This isn’t the first time a gambler has tried to get out of a major debt this way, and for a veteran gambler, it’s sort of a naïve argument,” says Aaron Duncan, an expert on gambling and pop culture at the University of Nebraska-Lincoln. “But it does also point to the contradiction of Las Vegas – that casinos sort of pay lip service to the notion of ‘what happens in Vegas stays in Vegas,’ that gambling has no consequences, but at the same time it’s all about free drinks to entice you to get into a less-than-best state of mind.”

To be sure, the regulations seem fairly clear. Nevada gaming law bars casinos from allowing “persons who are visibly intoxicated” to gamble, and also forbids serving complimentary drinks to someone who is obviously drunk.

As a result, the Nevada Gaming Commission is also investigating the casino, which opened late last year.

But even such seemingly straightforward regulations open up a massive gray area where dealers are forced to observe gamblers on a kind of inebriation spectrum. That stark reality – of casino operators plying gamblers with drinks pitted against gamblers’ personal responsibility to control themselves and their money – has led to lawsuits in the past.

An Encinitas gambler claimed in 2000 that he’d lost over $1 million because the casino kept bringing drinks. The parties settled over an undisclosed sum.

And in 2007, businessman Terrance Watanabe claimed he shouldn’t have to pay a $14.7 million debt to Harrah’s from a year-long drug and alcohol binge. After a long legal battle, the two parties settled, again on an undisclosed sum.

In Nevada, the stakes are high for gamblers who get into trouble. Unpaid debts are treated as criminal matters by Las Vegas prosecutors.

Johnston has admitted he had perhaps 10 drinks before hitting the casino, where he went on a 17-hour bender during which he claims to have “blacked out” and been unaware of what was happening to him.

The lawsuit says an unnamed former casino employee testified that Johnston was slurring his words and dropping cards. In past drunk-gambler cases there has been confusion around whether casino staff need to shut such gamblers off altogether or simply to ask them to refrain from gambling any more.

"My responsibility is, look, I had some drinks at the airport, on the plane. At some point, that's my responsibility," Johnston told CBS. "The unfortunate part about it for them is, they have a bigger responsibility than I do."

The Grand has not commented on the case.