The “Sophia Stripe” yoga legging—a purple, pink, and orange ombré pattern—that’s sold by K-Deer, a New Jersey-based luxury activewear company, is characterized in its online description as “one of a kind in every way.”

Perhaps that was true, until late December, when Gap Inc.’s athletic apparel brand Athleta started selling a yoga pant with a nearly identical print.

On December 27, Athleta featured its own purple, pink, and orange ombré tights—dubbed the “High Rise Bold Stripe Chaturanga Tight”—in an Instagram photo promoting the brand’s “new colors and patterns.” The black and navy versions of the tights also looked nearly identical to K-Deer’s “Jody” and “Alexis” stripe pants.

Shortly after Christmas, K-Deer founder Kristine Deer discovered the similarities between Athleta’s yoga pant prints and her own when she received a screenshot of Athleta’s versions. Deer, 30, who started her company out of her childhood bedroom four years ago, said her line of striped yoga pants—there are 11 different versions—are her bestselling products. She says she’s sold about 30,000 pairs in the past two years through the K-Deer website and at retailers worldwide. She says the “Jody” and “Alexis” versions have been in her collection for two years and the “Sophia” pattern was added to her fall collection in October.

“It was one of those jaw-dropping moments,” she told Fortune on Wednesday.

Deer wasn’t the only one to notice.

On the Instagram photo of Athleta’s Chaturanga Tight in “majestic purple” users left comments accusing Athleta of “knocking off” K-Deer’s stripe design. K-Deer fans also took to Facebook this week to point out Athleta’s apparent duplication of K-Deer’s print, using hashtags like #IStandWithKDeer and #BoycottAthleta.

What has upset Deer the most is that her striped leggings are designed with a “purpose,” which Athleta’s leggings don’t acknowledge. K-Deer’s “Sophia Stripe,” for instance, is named after Deer’s friend who’s cared for her ill mother. A portion of its sales is donated to the Vs. Cancer Foundation.

A day after Fortune contacted Athleta for this story, the company removed its striped pants from its website. “At Athleta, our customers always come first and, after hearing recent feedback on the High Rise Bold Stripe Chaturanga Tight, we have decided to remove it from our assortment,” Debbie Felix, spokeswoman for Gap Inc., told Fortune.

Deer says that she’s had no contact with Athleta and doesn’t plan to pursue legal action. “There’s nothing we can do from a legal standpoint. We can’t trademark a geometric print,” she says.

“Generally speaking, intellectual property rights have not provided fashion designers much protection,” says Nicole McLaughlin, a partner in the IP practice at Duane Morris, a law firm.

Fashion is not protected when it comes to the cut or shape of apparel items like a dress or skirt. That’s because clothing is considered a “useful article” under copyright law since it provides “intrinsic utilitarian function” by giving the wearer warmth or modesty. In 2012, New York Senator Chuck Schumer introduced a bill to extend copyright protection to fashion designs and revise the definition of “useful article,” but the measure died in the Senate.

Fabric prints, however, are a different story. They are, in fact, entitled to legal protection.

“When a designer [creates] a dress, the design of the cut is not protectable, but the pattern is because it’s separate from the usefulness of clothing,” McLaughlin says.

A fabric print can be copyrighted, trademarked, or patented. Securing copyright protection for a pattern is the easiest option since the moment a designer creates it, it’s automatically copyrighted, even without a registration.

“In order for there to be copyright protection, a design has to meet some standard of originality and non-functionality,” McLaughlin says. “A design [with] some kind of pictorial or graphic certainly overcomes that hurdle of originality. The Louis Vuitton checkerboard pattern is not crazy intricate,” she says, “yet it’s protected.”

To enforce a copyright, a designer must prove that another pattern is substantially similar to her pattern and that the other designer had access to her print. The latter requirement is typically a tough hurdle since it’s often heavily dependent on circumstantial evidence.

Trademark and patents are available to fashion designers, but they are more difficult to obtain and the process of securing them takes longer. By the time a designer gets either, the pattern they’re trying to protect may be out of style, McLaughlin says.

McLaughlin said that the similarities between K-Deer’s stripe leggings and Athleta’s “certainly raises one’s eyebrows.” But to make a legal case against Athleta, you would “have to determine that Athleta didn’t create the pattern themselves, independently,” she says. “It’s dangerous to make [accusations] until more questions are asked.”