Mr Justice Arnold is analysing a High Court argument between confectionery giants Nestle - which sells Kit Kat bars - and Cadbury.
Nestle wants to register the three-dimensional shape of a Kit Kat as a trademark. Cadbury has objected.
The judge heard legal argument from both sides at a hearing in London in December - and outlined his thoughts in a published ruling.
He said aspects of European trademark law were "unclear". And he said he would seek clarification from the Court of Justice in the European Union.
"Certain aspects of the relevant law remain unclear," said Mr Justice Arnold. "I have decided it is necessary to seek clarification of the law from the Court of Justice of the European Union in order to determine the (dispute)."