Ryanair has been ordered by Madrid’s mercantile court to return €20 it forced a passenger to pay when she took hand luggage on a flight from Madrid to Brussels.

The case came about after Ryanair introduced new charges for customers bringing anything more than one personal item into the cabin last year. Customers who don’t pay the €14 (£12) “Priority” customer supplement cannot take hand luggage exceeding handbags or a small rucksack with dimensions of 40cm x 20cm x 25cm.

The judge said airlines cannot charge for a hand baggage “suitcase whose dimensions and weight could perfectly be transported in the cabin”.

But Ryanair says the Spanish court’s ruling would have no impact on its fares as it would continue to charge for carry-on baggage items above its lower size limit. It claimed the ruling misquoted the European Court of Justice and misinterpreted the airlines’ commercial freedom to determine the size of cabin baggage.

The passenger who took the case to court paid €35.69 for a flight from Madrid to Brussels, and attempted to board with a handbag and a small suitcase, which fitted in the overhead baggage space and did not weigh more than 10kg. But she was told she had to pay extra as she had not bought a Priority ticket.

The judge said that Spanish transport regulations oblige airlines to include an allowance for cabin baggage within the air fare charged.

She also cited a 2014 ruling by the European Court of Justice in a case involving budget airline Vueling, which stipulated that carry-on baggage is “an indispensable element of the transport of passengers and, as such, cannot be subject to a price supplement,” as long as bags are within the correct dimensions.

Despite ordering Ryanair to return the passenger’s €20, the court rejected a claim for compensation.

The court said in a statement that its ruling cannot be appealed.

An investigation by Which? Travel in September found Ryanair charges the most for flight extras such as luggage, confirmed seats, and food and drink.