Acting defense secretary Patrick Shanahan arrives for a classified briefing with lawmakers on Capitol Hill on May 21, 2019. (Jonathan Ernst/Reuters)

Acting defense secretary Patrick Shanahan has mandated new restrictions on the way the Pentagon shares information with Congress about military operations around the world, a move that is straining ties with key Republican and Democratic lawmakers.

In a May 8 internal memo, which was obtained by The Washington Post, Shanahan lays out the criteria for when Pentagon officials may provide congressional offices or committees information they request about operational plans and orders.

The memo comes as lawmakers from both parties complain that the Trump administration has withheld information that prevents them from executing their constitutionally mandated oversight role. Some lawmakers are also concerned about whether Shanahan has allowed the military to be drawn too deeply into President Trump’s immigration agenda.

“Congress oversees the Department of Defense; but with this new policy, the department is overstepping its authority by presuming to determine what warrants legislative oversight,” Reps. Adam Smith (D-Wash.) and Mac Thornberry (R-Tex.), the chair and ranking Republican of the House Armed Services Committee.

The memo was shared widely inside the Pentagon but was sent to key lawmakers only after inquiries by The Post. It outlines a half-dozen guidelines, including requirements that military officials and political appointees evaluate whether the request “contains sufficient information to demonstrate a relationship to the legislative function.” The memo urges Defense Department officials to provide a summary briefing rather than a requested plan or order itself.

The memo appears to have been inspired by concerns that lawmakers, who have security clearances, will not safeguard military plans. It calls on officials to assess “whether the degree of protection from unauthorized disclosure that Congress will afford to the plan is equivalent to that afforded” by the Pentagon.

Sen. Jack Reed (R.I.), the top Democrat on the Senate Armed Services Committee, said the memo “seems to be another way in which they can claim that they don’t need to respond to legitimate inquiry of Congress.” Reed received the memo Saturday, shortly after The Post asked the Pentagon about it.

“From what I can glean from the memorandum basically they can use any factor they want to say no and they can make a determination what they think we need to do our job,” Reed said in an interview. “I think we’re better positioned to determine what we need to do our job.”

A defense official, speaking on the condition of anonymity to describe military officials’ thinking about the memo, said Pentagon leaders had been concerned about preserving the military chain of command and about the potential for congressional interference in what they consider to be an executive branch function, the formulation of military operations.

The official said that Congress had been most interested in learning more about Special Operations activities, which are among the most sensitive military operations but have also, in recent years, produced some of the biggest public backlashes.

“While I understand they’re not happy . . . we’ve gone from saying no to setting a process to adjudicate and consider saying yes,” the official said.

The guidelines represent a dramatic twist in a decades-long tug-of-war between the Pentagon and Congress over access to sensitive information.

While lawmakers routinely request information on a host of military matters, including weapons programs, personnel procedures and support to allies, they are also sometimes provided classified information about current or future military operations, which they are barred by law from disclosing.

The memo could complicate Senate confirmation hearings for Shanahan, who took over in January after his predecessor, Jim Mattis, resigned over differences with Trump. Shanahan is expected to appear before the Senate Armed Services Committee in June.

Lt. Col. Joe Buccino, a spokesman for Shanahan, said the new policy aims to increase “transparency and information sharing with Congress.”

Under Shanahan’s direction, Buccino said, “the Department of Defense has been engaging with the Senate and House Armed Services Committees to develop a process for providing Congress with access to plans and operational orders, including Executive Orders.”

While Trump has praised Shanahan, a former Boeing executive, numerous lawmakers have expressed skepticism about his ability to act as a counterweight to the president and his closest advisers in delicate matters of national security. Mattis labored to insulate the military from the country’s divisive politics and the White House, which won him plaudits from lawmakers but damaged his relationship with Trump.

Since taking on the top Pentagon job, Shanahan has presided over a deepening of the military’s involvement along the southern border, a mission Mattis viewed with skepticism but did not resist.

Some lawmakers see Shanahan’s decision to shift resources toward construction of a border wall, which has helped make up for Congress’ refusal to allocate funds for that purpose, as an effort to flout their prerogative.

In the new memo, Shanahan concentrates responsibility for evaluating congressional requests in the office of the undersecretary of defense for policy, which is typically led by a political appointee. Previously, officials across the Defense Department responded to requests on a more ad hoc basis, in keeping with what officials described as a “gentleman’s agreement” with lawmakers.

According to Reed, obtaining access to such information has become harder since Trump took office. Reed cited a 2017 operation in Niger in which four U.S. service members died, after which he said lawmakers had to “track down” the related operational orders and review the legal authorities under which troops were operating.

But officials from both the Pentagon and Capitol Hill agreed that a more formalized process for sharing information, if done in a mutually acceptable way, would be of value.

A former senior Pentagon official, who spoke on the condition of anonymity to speak candidly, said the memo did not appear to establish a more difficult process for routine congressional requests related to other oversight topics, including policy and budgetary issues.

“Rather, it appears to set an elevated, formal and mostly reasonable process relative to requests for a specific and especially sensitive subset of Pentagon materials provided the Pentagon doesn't seek to weaponize the process to frustrate a broader range of oversight requests, which would be deeply problematic,” the former official said.

Smith and Thornberry said they intended to address the sharing of operational information in this year’s defense authorization bill, which is now being drafted.

They appeared particularly galled by the memo’s suggestion that Congress might make sensitive information public, which they characterized as “inexcusable and inaccurate.”

“The Department is not in a position to evaluate defense committees’ worthiness to receive classified information, nor characterize our ability to appropriately protect it,” they said.