In a move likely to exacerbate already strained relations between Congress and the Pentagon, the government’s former chief prosecutor in Guantanamo was barred from testifying Tuesday before a Senate Judiciary subcommittee.

Col. Morris Davis, who resigned Oct. 4 as the government’s top lawyer on military commissions but remains in the military, was prohibited by the Defense Department from testifying before the Judiciary Subcommittee on Terrorism, Technology and Homeland Security, chaired by Sen. Dianne Feinstein (D-Calif.).

Feinstein said she was “disappointed” by the move, and a spokesman for the Senator said she had no plans to issue a subpoena for Davis’ testimony right now, but is leaving her future options open.

The Senator told Roll Call that the Pentagon’s decision, however, “sets a very bad precedent” similar to the White House refusing to provide witnesses and testimony to Congress in the U.S. attorneys probe.

“We assured the administration that Col. Davis would not be asked about pending and open cases, but we were told simply that Col. Davis was active duty military and because he was active duty military, they could issue an order that he had to follow,” Feinstein said at the hearing.

“Unfortunately, I have to conclude that by prohibiting Col. Davis from testifying, the administration is trying to stop a fair and open discussion about the legal rights of detainees at Guantanamo,” she added.

In an interview, Davis said he first heard that his bosses would issue an order barring him from testifying from Feinstein’s counsel on Dec. 6. He then got a verbal confirmation of that order from the Pentagon’s legislative affairs shop.

“I was surprised it took them that long to do it,” Davis said. “The last thing they want is for me to talk.”

“My intention was to go there and tell the truth. If they’re so concerned about that … what other things are out there?” Davis asked.

Davis, who now is the head of Air Force judiciary, said he resigned as chief Guantanamo prosecutor on Oct. 4 after it became clear that political appointees such as Pentagon General Counsel William Haynes would be in his chain of command.

Though the military prohibited Davis from testifying before Congress, he has given various interviews to the press this week, including to “NBC Nightly News” and Canadian radio. He also wrote a Dec. 11 op-ed for the Los Angeles Times explaining why he thinks military commissions cannot operate fairly.

Davis said he called the Pentagon public affairs office to vet the interview requests but never heard back.

Defense Department spokesman Lt. Col. Brian Maka on Tuesday defended the Pentagon’s decision to bar Davis from going to the Hill, saying the department provided the “best-informed and most capable witness for hearings on this topic.”

“Former military commission staff members have no role in presenting testimony on the Defense Department’s behalf,” Maka said.

In this case, the military’s hand-picked witness was Air Force Brig. Gen. Thomas Hartmann, the legal adviser to the administrator of the trials. At the subcommittee hearing, Hartmann called the controversial commissions and their procedures, designed to try suspected terrorists, “unprecedented,” “fair” and “factual.”

But at least one Republican, Sen. Lindsey Graham (S.C.), seemed frustrated, pushing away the microphone when Hartmann refused to answer a direct question from Graham about whether waterboarding constitutes torture.

“I am not equipped to answer that question, Senator,” Hartmann demurred.

This is not the first time there has been a conflict over military testimony since Democrats took control of Congress and stepped up their oversight of the Bush administration. In April, a Pentagon lawyer interrupted the testimony of junior Army officers before a House Armed Services subcommittee, saying they were not allowed to speak while being transcribed.

Assistant Secretary of Defense for Legislative Affairs Robert Wilkie on June 27 withdrew a previous memo restricting testimony by military officials before Congress.

“We will endeavor to do what we can to assist you as we carry on your important new duties,” wrote Wilkie, a one-time aide to Sen. Trent Lott (R-Miss.) and former Sen. Jesse Helms (R-N.C.).

Eugene Fidell, a Yale University professor of military law and president of the National Institute of Military Justice, said Congress should act in this case.

“This skirmish strikes me as extremely ill-advised. If I were a Member of Congress, I would be beside myself about this,” Fidell remarked. “Our elected officials cannot do their jobs in the way we expect of them if they cannot inform themselves.”

“If this is allowed to stand, it will be another step in that erosion.”

The irony is that Davis was once one of the administration’s staunchest defenders of the terrorist detention site known as Gitmo, saying that suspected terrorists could get a fair trial there.

But Davis chafed against the authority of Hartmann, whom he accused of overstepping his bounds as the top legal adviser on the controversial military tribunals. He claimed Hartmann should not be permitted to become involved in prosecutorial decisions.

Since they were established, only one detainee has been through the system of military commissions and that was with a plea deal. But the administration hopes to eventually try as many as 80 of about 330 detainees there, a handful of them “high-value” suspects.

Erin P. Billings contributed to this report.