What’s the line between a brand following a trend and outright copying a design? That’s the question at the center of a new lawsuit filed by Lululemon against Costco.

The athleisure brand claims the wholesale retailer ripped off designs of its popular sweatshirts and pants. The case taps into a broader cultural moment: the rise of “dupe” culture, which has taken over social media.

From fragrances to fashion, TikTok and Instagram are filled with influencers touting affordable alternatives to luxury goods.

Call it a dupe, a copycat or a knock off, though the trending term has changed over the years, the idea has been around for a long time. Sarah Fackrell is a law professor at Illinois Tech. 

“This is nothing new,” Fackrell said. “This is one reason why we even have design patents in the first place.”

Design patents are meant to protect the appearance of a product — its shape, pattern and overall look. But proving in court that a design has been copied is no easy task.

“You gotta prove that someone’s going to look at that jacket and think that it was made or sponsored or approved by Lululemon, just on how it looks,” Fackrell said.

That standard is highly subjective. And once a lawsuit is filed, it opens the door to even more gray areas. Is a Ford Bronco a dupe of a Jeep? Is Pepsi a dupe of Coke? Where does inspiration end and imitation begin?

“If you look across all of retail, 95% of all things are duplicates, 5% are innovation,” said Christopher Durham, president of the Velocity Institute, a consulting firm focused on private label strategy.

Durham argues that imitation is how trends move and evolve. He also said copycat culture is ultimately good for consumers — more options, lower prices. And today’s shoppers are embracing private label products more than ever. Once embarrassed to be seen with off-brand cereal, many now actively seek out alternatives.

Think: Kirkland at Costco, the Sephora Collection, or Target’s Good & Gather.

“Trader Joe’s has been making Joe Joe’s for 50 years,” Durham said. “That recipe is just different enough that they don’t get sued. And honestly, a lot of people think the Joe Joe’s are better than the Oreos.”

With private labels booming and design mimicry more accepted, some companies may increasingly turn to lawsuits as a form of protection. Jan-Benedict Steenkamp, a marketing professor at the University of North Carolina at Chapel Hill, said it’s about market share.

“Every percentage point of market share that you lose to a private label really bites into your bottom line,” he said.

Steenkamp noted that while lawsuits like Lululemon’s don’t always win in court, they can still serve a purpose.

“Not because they necessarily will win them all,” he said, “but because enough legal action can scare other copycatters away.”

In other words, brands might not be able to stop all the copycats — but they can try to shift the target.