According to The Fashion Law, Nasty Gal unknowingly posted a photo of Swift to its social media accounts, in a design from Balmain's spring collection, using the hashtag #NastyGalsDoItBetter. Commentators were quick to call out the mistake, causing Nasty Gal to remove the post.
Neither Nasty Gal nor Balmain immediately responded to request for comment.
Read MoreLaw of the bargain: What you're really getting
Thanks to the rise of fast-fashion labels, which produce mass quantities of merchandise on a tighter time table, and the ubiquity of instant runway images on social media, looks that are knocked off from the catwalk often arrive at mass retailers before the originals hit the shelves. They're also sold for thousands of dollars less. While a Balmain jumpsuit could set shoppers back $6,000, Nasty Gal's version retails for $78.
Susan Scafidi, founder and academic director of Fordham University's Fashion Law Institute, said there are two ownership questions at stake in this instance: Taylor Swift's and Balmain's. Legally, she said, Nasty Gal could risk a false advertising or right of publicity claim by jumping to conclusions about the label. If it were to continue using Swift's name or image to promote the item, the performer would have a cause of action against the firm. Knocking off the Balmain original and selling it, however, is legal.
"French law extends copyright protection to fashion designs, and many other countries give some form of protection to fashion, but U.S. law generally does not," Scafidi said. "Over the past decade, creative American designers have introduced several bills in Congress that would give their designs protection similar to that of their European counterparts, but so far without success."
For its part, Balmain doesn't seem to have any bad blood toward fast-fashion retailers. The Paris fashion label and H&M on Monday announced an upcoming collaboration that will hit the retailer's stores in November.
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