Mr Justice Birss said Topshop's sale of a Rihanna T-shirt at the centre of the dispute was an act of " passing off".
But he said the "mere sale" of a T-shirt bearing the image of a famous person was not necessarily an act of "passing off".
He said a "substantial number" of buyers were likely to have been deceived into buying the Rihanna T-shirt because of a "false belief" that it had been authorised by the singer.
The judge said that was damaging to her "goodwill" and represented a loss of control over her reputation in the "fashion sphere".
He said it was for the singer not Topshop to choose what garments the public thought were endorsed by her.
More top news
Footage of a gun battle between Peruvian authorities and suspected drugs traffickers in which a plane was shot down has been released.
Orlando Bloom has visited children whose school was destroyed by shellfire during the conflict in Ukraine.
Jeremy Corbyn has launched a fresh attack on "ideological" Conservative cuts ahead of Thursday's elections.