Story highlights Mark A. Johnston says he was victimized in old Las Vegas hustle

"This is about you almost killing me," he says of casino's free drinks

Nevada gaming board is investigating whether Downtown Grand broke regulations

Newly opened Downtown Grand declines to comment

A California man who lost $500,000 at blackjack and pai gow is suing a new Las Vegas casino, alleging he was too drunk to be allowed to gamble over a 17-hour period just before Super Bowl weekend.

Mark A. Johnston of Ventura, California, is claiming he shouldn't have to pay the Downtown Grand Las Vegas Hotel & Casino the $500,000 debt because employees served him so much alcohol that he suffered a blackout and was unable to remember the losses or even his gambling, the lawsuit alleges.

In an interview Thursday with CNN, Johnston contended he was plied with liquor and victimized in an old-time hustle.

"Just picture a drunk walking the street and he's drunk, and someone pickpockets and takes his money from him. That's how I characterize it," Johnston said. "I feel like it's the days of old Vegas, the way they've been extorting me with letters and attorneys."

JUST WATCHED Man suing casino over $500K bill Replay More Videos ... MUST WATCH Man suing casino over $500K bill 03:14

The casino, which opened last November, declined to comment on the lawsuit, citing pending litigation, said spokeswoman Nicole Neal.

JUST WATCHED 'Blackout' drunk sues casino over $500K Replay More Videos ... MUST WATCH 'Blackout' drunk sues casino over $500K 01:54

Johnston said that he's not being a bad loser.

"I am not a sore loser. I've lost half a million. I've lost 800,000. I've lost a lot of money. This has nothing to do with that," the veteran gambler said. "Obviously I can afford what I lost."

Johnston, 52, a former owner of a Los Angeles car dealership, was standing beside his $250,000 Mercedes-Benz as he insisted his lawsuit was about a bigger issue.

"This is about you almost killing me," Johnston said. "What if I had gone to bed that night, with all those drinks in me, and I threw up on myself and I choked and died?"

Johnston acknowledged some responsibility for his drinking -- as many as 20 drinks while gambling over 17 hours on top of about 10 drinks before even stepping into the casino.

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

Johnston was referring to how the casino must follow Nevada laws on how complimentary drinks are given to gamblers.

In fact, the Nevada Gaming Control Board is now investigating the Downtown Grand, formerly the Lady Luck Casino, on whether it violated gaming regulations, said Karl Bennison, chief of the board's enforcement division.

Those regulations prohibit casinos from "permitting persons who are visibly intoxicated to participate in gaming activity" and from providing "complimentary service of intoxicating beverages in the casino area to persons who are visibly intoxicated."

"We are investigating this thoroughly," Bennison said. "We are aware of this matter. We'll see if there are regulation violations."

The casino could face a license revocation or fines or both if the violations are substantiated, Bennison said.

Neal, the casino spokeswoman, also declined to comment about the state investigation.

Johnston, a frequent gambler in Las Vegas, had always been a cash player at casinos and was never issued a line of credit more than $25,000. Still, in the past 10 years, he had never drawn on any casino line of credit, the lawsuit said. He worked in real estate and car sales and was the owner of a Mercedes-Benz dealership in west Los Angeles.

During Super Bowl weekend, however, he and a female friend flew from the Burbank, California, airport to Las Vegas, and he had consumed several alcoholic drinks by the time the couple ate dinner at a restaurant run by the Downtown Grand Casino, according to a sequence of events described in the lawsuit.

At dinner, Johnston was visibly drunk, which was also observed by an old friend, a law professor at the University of Nevada at Las Vegas who joined the pair for dinner.

Johnston was so inebriated that he had no recollection of leaving the restaurant on January 30 or the subsequent 44 hours, when he gambled in the casino and took out markers totaling $500,000.

He lost all that money at the Chinese domino game pai gow and at a private blackjack table during 17 hours of uninterrupted gambling and drinking, until the late afternoon of the following day.

Johnston takes prescribed medication that increases the intoxicating effects of alcohol, and a casino host who invited Johnston to the Downtown Grand was aware of Johnston's use of the medication, the suit alleged.

"Mr. Johnston, an experienced gambler, was dropping chips on the floor, confusing chip colors, and slurring his speech badly, and he was unable to read his cards or set his hands properly," the lawsuit said.

"To her shock, after sleeping for seven to eight hours, (Johnston's female friend) found Mr. Johnston still gambling at the blackjack table, and still heavily intoxicated, late in the afternoon of January 31, 2014," the suit said.

The suit recounts how Johnston took out two lines of credit for $100,000 each in the span of 21 minutes after 2 a.m. on January 31.

By 10:52 a.m., Johnston had taken out a third marker, for $50,000. Almost two hours later, he signed another marker for $250,000, the suit said.

Johnston lost it all. Moreover, the casino allegedly reneged on providing Johnston with a 20% discount on repaying the $500,000, which would have reduced the debt to $400,000, the lawsuit claimed. The casino also allegedly demanded that Johnston repay the $500,000 debt 46 days early, before a March 31 deadline, said the lawsuit, which was filed in February.

In the days after losing the $500,000, Johnston went to the Hard Rock Hotel and Casino, one of his preferred Las Vegas gaming destinations, but a Downtown Grand representative called the Hard Rock and told them of Johnston's debt, cautioning them about doing business with Johnston and "sullying Mr. Johnston's good name in the process," the lawsuit said.

The lawsuit seeks to nullify the gambling losses and seeks compensatory as well as punitive damages "in an amount sufficient to deter the Downtown Grand from similar conduct in the future," the suit said.