A German whisky called Glen Buchenbach may be infringing the protections given to Scotland’s national drink, even though its label makes clear the spirit is distilled in Germany, the EU’s top court has ruled.

The European court of justice took no final view on the case on Thursday, referring a complaint from the Scotch Whisky Association (SWA) back to German judges to make a ruling.

But in answering the Hamburg court’s query, it offered guidance to assess whether the German distiller Michael Klotz’s branding overstepped EU law on protected regional labels.

“Scotch whisky” can only be sold in the European Union if it is actually made in Scotland, for which the spirit is the biggest international export earner. Klotz’s “Swabian single malt whisky”, distilled near Stuttgart, is labelled as made in Germany. But the SWA argued that the use of the Gaelic term “glen” – a valley – could mislead buyers to think it was scotch.

The ECJ said the German court must decide whether the “average European consumer” would make that error.

It stressed that it was not enough for the word “glen” to evoke some kind of association with Scotland. It must actually bring to mind scotch whisky. But it did not matter, the court added, that the label said the product was made in Germany.

As with many of Europe’s hundreds of protected geographical designations, such as France’s champagne sparkling wine or parmesan cheese from Italy, Scottish distillers are vigilant of their branding; whisky accounts for 20% of UK food and drink exports, and about 40,000 jobs.

However, the UK’s imminent departure from the EU has raised some questions about those protections. In principle, London and Brussels say they hope to continue recognising each other’s labelling rules, but negotiations are ongoing.