The European Court of Justice has ruled that Uber should be regulated as a transport firm after finding it formed "an integral part of an overall service whose main component is a transport service".
Uber has said this ruling will not affect its UK operation, and argues it is a technology service enabling people to contact each other, rather than operating as a taxi service.
The case stemmed from a claim by Barcelona taxi drivers, who said Uber drivers should be licensed.
While the ruling could lead to changes in the way the firm operates in some European cities, Uber has insisted there will be no change to their operation in most countries, including in the UK.
Uber and its drivers already require licences from local authorities to operate in the UK.
The firm's license to operate in London expired in October and has not been renewed amid concerns for passenger safety.
While Uber appeals against this decision, drivers will still be allowed to operate in the city.
Keep up to date with the latest news in west London via the free getwestlondon app.
You can even set it to receive push notifications for all the breaking news in your area