United Launch Alliance (ULA) has declined to bid on the launch of a next-generation GPS satellite, opening the way for SpaceX to launch its first national security payload later this decade. ULA’s decision marks the latest (apparently triumphant) skirmish in a contentious, high stakes battle by the upstart SpaceX to win contracts to launch Pentagon satellites.

The Air Force asked for bids to launch a GPS 3 satellite, which has improved signal accuracy and anti-jamming capabilities, in 2018. Monday was the deadline to submit bids. This was the first military contract for a launch since the Air Force certified SpaceX for satellite launches in May, a move that allowed it to compete with ULA.

A joint venture between Lockheed Martin and Boeing, ULA has had a sterling record with its Atlas 5 rocket, with more than 100 successful launches. However, the rocket relies on the Russian-manufactured RD-180 engine for its thrust, and given the ongoing tensions between the United States and Ukraine, the US Congress passed a law last year banning the use of these engines beginning in 2019.

ULA’s chief executive, Tory Bruno, told the Washington Post that his company was “unable to submit a compliant proposal” because of contract requirements and the limitations Congress has imposed on the RD-180 engine.

The company’s decision appears to bring some closure to the public and legal battle SpaceX launched in April, 2014, to buttress its efforts to get into the national defense satellite launch market. At the time, SpaceX CEO Elon Musk accused the US government of entering into improper and uncompeted launch agreements with private contractors and said that SpaceX’s rockets could do the same job at a far lower cost. “We’re just protesting and saying these launches should be competed," said Musk at a press conference. "And if we compete and lose, that’s fine, but why were they not even competed?"

After SpaceX filed a lawsuit against the Air Force to allow it to compete for national security launch contracts, the two sides resolved their differences and the Air Force promised to review the company’s certification application expeditiously. It finalized that process in May.

Meanwhile, with a limited amount of RD-180 engines on hand, ULA has been working with Blue Origin to develop a new, American-made rocket engine, the BE-4, for its next generation rocket, Vulcan. Officials with ULA have said they hope to perform the initial Vulcan test flight in 2019, but certification for that rocket will likely take considerably longer.

That’s why the company has asked Congress for additional access to the RD-180 engines, but so far they’ve had little luck. Addressing the issue in a flood speech in June, US Sen. John McCain (R-Ariz.) said, “We must not reward Vladimir Putin and the Russian military industrial complex.” That view is shared by a number of his colleagues.

ULA has another rocket, the Delta 4, which does have American engines. However, its launch costs are prohibitively more expensive than the Atlas 5, and even more so than SpaceX’s Falcon 9 rocket.

For SpaceX, getting its foot in the national security launch door could prove quite lucrative. The 2018 launch sought by the Air Force is the first of nine similar launches that the military is expected to put up for a bid by the end of 2017.