High Court Justice Colin Birss says buyers were likely deceived by believing she had authorized its sale.
Birss says the sales represented a loss of Rihanna's reputation in the fashion realm, where the singer has been trying to carve out a name as a designer. She has a clothing line in her name at a rival store.
The shirts were first sold as the "Rihanna Tank." After her complaints, they were sold as being the "Headscarf Girl Tank" and the "Icon Tank."
The judge did not make an assessment of damages in his ruling Wednesday.