The Air Force won’t stop United Launch Alliance (ULA) from divesting its Delta IV Heavy rocket, despite a pair of key lawmakers ordering the service to do so.

“That was a memo to us and not a law or language,” Assistant Secretary of the Air Force for Acquisition, Military Deputy, Lt. Gen. Arnold Bunch told reporters last Thursday after an Air Force Association breakfast in Arlington, Va. “Industry is making their decisions. I don’t have the ability…to tell them what they can, and can’t, do.”

House Armed Services Committee (HASC) Chairman Mac Thornberry and HASC strategic forces subcommittee Chairman Michael Rogers (R-Ala.) said in a Feb. 28 letter to Air Force brass that ULA is allowing the phase out of the Delta IV Heavy capability before there is a certified, reliable replacement launch system available. The two lawmakers, in the letter, tell the Air Force to stop this. Thornberry’s spokesman did not return a request for comment Friday.

ULA has no plans on divesting its Delta IV rocket. Company spokeswoman Jessica Rye said Friday ULA will ensure there is no gap in assured access to space by continuing to offer the Delta IV Heavy until the Air Force completes and selects two new launch providers. Delta IV Heavy launches the Pentagon’s heaviest satellites, which are often spy spacecraft for the National Reconnaissance Office (NRO).

SpaceX is developing its own heavy lift vehicle, Falcon Heavy, but this rocket has yet to debut. Company spokesman John Taylor said Friday Falcon Heavy was set to debut later this year.

ULA CEO Tory Bruno told a House panel in March 2015 he planned on retiring the Delta IV launch vehicle in the 2018-2019 timeframe because, at between $400 million to $600 million per launch, it simply wasn’t competitive on an open market. Rye said he was referring to Delta IV medium, which will launch the Air Force’s ninth Wideband Global SATCOM (WGS-9) rocket Saturday night (Defense Daily; March 18, 2015).

Delta IV Heavy launches are the most expensive launches available to DoD. The Air Force on Dec. 2 awarded ULA a $269 million contract to execute a requirement for fiscal year 2017 launch vehicle production services in support of the Delta IV Heavy.

ULA is a joint venture between Boeing [BA] and Lockheed Martin [LMT].