Uber on Thursday said it filed a complaint with the European Union over legislation in Hungary that caused the on-demand ride service to stop operating in that country.
The move came a month after Uber suspended service in Hungary, blaming new legislation it claimed made it "impossible" to operate.
It was the first such halt of Uber in an EU country and came in reaction to a law that allows Hungarian authorities to block "a provider of taxi services operating without a proper dispatch center" for up to one year.
An Uber statement at the time said that the legislation passed by parliament "makes it impossible for Hungarian drivers, in spite of having licences and properly paying taxes, to use their own vehicles to make money."
The US company has become one of the world's most valuable startups, worth an estimated $68 billion, as it has expanded to more than 50 countries including 21 EU member countries other than Hungary.
But it has faced regulatory hurdles and protests from established taxi operators in most locations where it has launched.
Since Uber entered the Hungarian market in November 2014, around 1,200 drivers and 160,000 riders have registered with the company.
The new law followed months of protests by licensed taxi drivers who have complained that orders have been decreasing sharply.
They say Uber drivers -- who often charge significantly cheaper fares -- should be subject to the same stringent rules regulating official cabs.
Uber on Thursday said it turned to the EU to investigate what it saw as "a clear breach of the fundamental principles of the European Single Market."