(Reuters) -A French union filed a legal challenge on Monday against a decision by the country's telecoms regulator to grant radio spectrum to Amazon's ( AMZN ) satellite internet service, the biggest test yet of the U.S. tech giant's broadband ambitions.

The CFE-CGC Telecoms union said it had asked France's highest administrative court to annul a July decision by regulator Arcep to award Amazon ( AMZN ) 10-year rights to frequencies for its low earth orbit (LEO) satellite network.

The union argued that Arcep did not conduct a market analysis before awarding the spectrum and failed to consult France's competition authority. It also questioned why the watchdog did not require a competitive bidding process for the scarce frequencies.

Amazon ( AMZN ) and Arcep declined to comment.

The legal battle is another example of France confronting large U.S. technology firms at a time when satellite operators race to secure valuable spectrum licences.

Amazon ( AMZN ) plans to deploy a fleet of over 3,000 LEO satellites, previously known as Project Kuiper, with select enterprise services slated to begin in late 2025 and broader rollout expected in 2026.

The first 27 satellites were launched in April.

The union also raised security concerns, saying Arcep did not address public safety legal requirements or data protection issues for a non-European operator, which it said carried national security and emergency communications risks.

Advisory firm Oxford Economics, in a study commissioned by Amazon ( AMZN ) earlier this year, projected France to benefit the most from Kuiper, particularly through contracts with space launch provider Arianespace.

Competing in the emerging LEO broadband internet market are Elon Musk's Starlink and France's Eutelsat, with fleets of 8,000 and 648 satellites, respectively.

Concerns over European dependence on Starlink grew this year after fears emerged that access to the service, key to Ukraine's military communications, could be pulled.

Starlink, which reports 8 million global subscribers but does not disclose country-specific figures, secured a similar 10-year licence in France in 2021.

"We didn't see (Starlink) coming," said Sebastien Crozier, chairman of the CFE-CGC union at Orange.

"They granted them a licence, and we no longer know how many subscribers they have."