In what could be another setback in the European Union, a senior adviser to the region's highest court said that Uber should have to abide by rules governing taxi services, and backed a French law that led to sanctions for the ride-hailing service 's top managers in the country.

The EU court is being asked to give guidance on the legality of changes made to a 2014 French law, which Uber says is targeting apps such as UberPop.

EU nations "may prohibit and punish the illegal exercise of a transport activity such as UberPop without having to notify the" European Commission of the draft law, Maciej Szpunar, an advocate general for the Court of Justice of the European Union said, rejecting Uber's claims that the rules were invalid because France didn't notify the EU in advance.

The recommendation is a non-binding opinion but as several publications are noting, judges generally follow the advice of their advocates general.

Uber says it will wait for the final ruling later this year and says the law refers to a service using unlicensed drivers known as UberPop, which it had already discontinued in France after a series of strikes. The company was fined nearly $500,000 for running the service in a separate case.

UberPop is essentially a legal workaround attempted by Uber in countries where it's legal to "ride share" and have the passenger pay a part of expenses, but not to make a profit. Furthermore the driver doesn't need to be licensed to offer professional transportation services. UberPop was meant to fall into this category but it wasn't technically ride "sharing", since the passenger decides the destination, and while it was a low-cost Uber category it was still for profit.

Uber currently works only with professional licensed drivers in many of its main European markets.