Spain's Supreme Court ruled on Friday that Ryanair's luggage rules, under which the budget carrier can send bags and suitcases on a different flight than passengers, were unfair.
Following a complaint from a consumer association, the court said there may be cases that justify sending luggage on a separate flight, but that Ryanair's clause was too generic.
"(It leaves) to the will of the carrier to send the checked baggage on the same flight (as the passenger) or not under ... unspecified and absolutely unspecific circumstances of safety or operation," it said.
Irish carrier Ryanair did not immediately respond to a request for comment.
The Supreme Court also reaffirmed a previous ruling which annulled other clauses, including a 40 euro charge for reprinting a boarding pass, which it deemed disproportionate.
In 2019, it ruled that it was unfair for Ryanair to charge a fee for hand luggage.