Lawsuits over dupes are popping up in courts. But can dupes be illegal?

To customers, a lookalike to Ugg's Tasman slippers or a knock-off of Lululemon's ultra-popular Define jacket can be a fantastic bargain. But to the companies that make the original products, similar-but-cheaper items can be bad for business.

While knock-offs are nothing new, dupes — short for "duplicate" — have exploded in popularity in recent years. And for many younger buyers, buying an imitation is no longer something to hide.

"A lot of the consumers that we're seeing on social media, on TikTok, are so proudly displaying the dupes that they found, kind of as a badge of honour. That stigma really isn't there anymore," said Julie Zerbo, editor-in-chief of fashion publication The Fashion Law.

The rise of dupes has also brought a corresponding wave of lawsuits from companies, saying copies of their products shouldn't be allowed to exist.

American Eagle, Sol de Janeiro, Benefit Cosmetics, Deckers Brands (Ugg's parent company) and Supergoop are just a few of the fashion and beauty companies on that list. Vancouver-based Lululemon became a recent entrant when it sued Costco late last month over three products it said were knock-offs of its clothing.

But are they actually illegal? Intellectual property experts say it really depends on the rights a company has over a product, and whether customers can tell the difference between the original and its copycat.

The term "dupe" itself has been appearing more in legal filings, says Alexandra Roberts, law and media professor at Northeastern University — including in Lululemon's against Costco. That could partially be because their appeal has grown among online shoppers.

"Where in previous years, a company might have just said, 'Oh, this looks to us like trademark infringement,' here, [brands] are kind of building a case around the idea of [a] dupe," Roberts said.

"The fact that something is perceived as a dupe ... that all works its way into the allegations."

WATCH | Trying to beat online fashion copies:

Local belt maker Unbelts has a new strategy for beating online "dupe" makers it believes are ripping off its product. The company has developed a totally local supply chain. Unbelts owner Claire Theaker-Brown joins us to discuss the strategy.

Loren Mallett, an intellectual property lawyer in Vancouver, says any case where a company says it's been copied largely depends on the rights it has over its product.

Patents, industrial designs and trademarks can all protect certain parts of an item — but a company has to formally register elements like its logo or packaging design. If it hasn't, it's probably out of luck, Mallett says.

And even if it has, it still might be OK to sell something really similar. The legality of a dupe depends on whether customers could be confused by the two items and think they are the exact same, Roberts says.

In Lululemon's case, for example, the question might be whether buyers of the Costco sweatshirt thought they were purchasing Lululemon's Scuba hoodie, Roberts says.

She says people tend to like dupes specifically because they aren't the real deal, but a cheaper alternative. And for that reason, she says, many may not be successfully litigated against.

LISTEN | Dupe culture: Why Gen Z is embracing fakes:

While we don't necessarily think of them as dupes, generic brands — think Life brand products sold at Shoppers Drug Mart, or Walmart's Great Value — have occupied this space for a long time, Roberts says. And historically, courts have allowed them because customers understand that one is meant to be a cheaper alternative to the other.

Mallett adds that the conversation around dupes could impact companies like Lululemon in court, as many customers have said online that some of Costco's products look just like Lululemon's. The athleisure company will likely argue this as evidence that Costco wanted to pass off its product as a Lululemon item — whereas Costco will likely say it is proof the customer knew for a fact they were buying a similar-looking alternative at a lower price, according to Mallett.

Zerbo says many dupe-related cases are still making their way through courts. But there are some resolved ones where the lookalike has come out on top.

She points to a recent conflict in the U.S. between Steve Madden and Ganni as a good example. Danish footwear brand Ganni sent cease-and-desist letters to some companies that sold certain Steve Madden shoes, saying they looked too similar to its own buckle ballerina flats and two-strap sandals.

But Steve Madden turned around and sued Ganni, saying it had no right to tell those retailers they couldn't sell the similar Steve Madden shoes, because there was "nothing new or original" about a shoe made of leather and that has straps, eyelets and buckles — common elements in lots of footwear. Ganni ultimately walked back its original legal threats, Zerbo said, and even agreed not to sue in the future over the shoe designs. (Ganni was more successful in its home country of Denmark, however.)

Zerbo says these cases show how courts generally don't want monopolies, and try to prevent giving a brand that kind of power.

"That would be bad for competition, that would be bad for consumers, prices would go through the roof."

Zerbo says duping is unlikely to slow down anytime soon, as many shoppers love a good deal.

She says history is full of copycat designs, which have largely been allowed to exist. Take fast fashion, for example. Companies like H&M and Forever 21 became giants mainly by replicating runway elements for a cheaper price.

"It's such a big market. There's so much consumer demand for dupes that companies would be hard pressed to stop trying to make them."

If anything, she says some luxury brands have relied on their name to appeal to customers, and have "rested on their laurels" rather than innovating.

"And companies can't afford to do that anymore."