It's the craft beer lover's equivalent of the going to school naked nightmare.

For years, home brewer Evan Parent claims he bought Blue Moon beer for friends and family, safe in the knowledge it was independently brewed and handcrafted.

But then — horror of horrors — the San Diego beer aficionado says his friends told him he'd been sipping from the enemy's cup.

"Blue Moon is not a craft beer, but rather a mass produced beer made by MillerCoors," Parent says in a California class action lawsuit.

"Through its false and deceptive marketing, [the company] misleads consumers to believe that Blue Moon is an independently brewed, handcrafted beer."

'What's the big deal?'

It's hard to say exactly what's more symbolic of craft beer's battle to stay grassroots: the fact a man would sue for being tricked into buying mainstream suds, or the allegation one of North America's largest breweries would try to lure hipsters with faux craft credentials.

But Parent's case highlights fears of true beer believers as major breweries watch rapidly expanding craft producers eat into their bottom line.

A California beer drinker's lawsuit claims Blue Moon beer is not actually craft beer.

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"There is the question of 'So what? They purchased the beer, they received the beer, they drank the beer. What's the big deal?'" says Parent's lawyer, James Treglio.

"The big deal is: 'Yeah, but they charged more for it.'"

The lawsuit claims identifying Blue Moon as a craft beer allows MillerCoors to charge up to 50 per cent more for the beer than its other products.

What is craft beer anyway?

Although beer consumption has dropped overall in Canada in recent years, sales of craft beer have grown to between six and 10 per cent of the market.

Toronto beer blogger Ben Johnson says major breweries are moving in two different directions: buying existing craft brewers or coming up with craft-like products like Blue Moon or its Anheuser-Busch InBev competition Shocktop.

​While he can understand the financial incentive for small companies to sell out, he can't blame drinkers for viewing their beer with suspicion once they do.

"It's like when your favourite band signs to a major label and suddenly they're filling stadiums," he says. "It's not quite the same thing as when you went to see them at the bar when you were in high school."

Humber College School of Hospitality instructor Roger Mittag says part of the problem is that there is no hard and fast definition of craft beer. Or of what constitutes a small brewer.

"Our definitions are so wide and varied, it would make your head spin," says Mittag, founder of the beer education company Thirst For Knowledge.

"In Saskatchewan, in order to be classified as a small brewer, you have to brew below 5,000 hectolitres. In New Brunswick, it's below 1.5 million hectolitres."

The B.C. Craft Brewers Guild represents independent, B.C.-owned breweries which produce less than 160,000 hectolitres of beer a year.

On The Coast beer columnist Rebecca Whyman says people have a right to know where their beer comes from. (Stephen Quinn)

But Mittag says major breweries can also produce quality beer.

"In my eyes, craft beer is about passion, and it's about creating beer with flavour and aroma that is different than what we would have considered to be the mainstream," he says.

"It takes time, and it takes thought, and there are big brewers that can do that."

B.C.'s tasting rooms

But a big part of craft beer's allure lies in its local origins.

From 2013 to 2014, sales of craft beer grew in B.C. by 37 per cent.

A concentration of tasting rooms has spawned a tourism industry on Vancouver's East Side. And the explosion of new craft breweries has infused the province's beer scene with energy and investment.

CBC Radio's On The Coast beer columnist Rebecca Whyman says people like to know where their money is going.

"I don't want to see any of the big guys go under," she says.

"I just want people to know where their beer comes from. The craft beer movement's really about integrity and honesty and transparency. In the tasting rooms, you can actually go and meet the brewer. You're not going to get that from a macro-brewery."

For its part, MillerCoors claims Parent's suit is without merit, noting Blue Moon's 20-year history of brewing "creative beers of the highest quality."

"MillerCoors is tremendously proud of Blue Moon and has always embraced our ownership and support of this wonderful brand," the company says in a statement.

And, it could be argued that men like John Molson, John Kinder Labatt, Adolph Coors and Frederick Miller were the original craft brewers.

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