Donald Trump. Getty Images President Donald Trump signed a presidential memorandum Saturday that removed the nation's top military and intelligence advisers as regular attendees of the National Security Council's Principals Committee, the interagency forum that deals with policy issues affecting national security.

The executive measure established Trump's chief strategist, Steve Bannon, as a regular attendee, whereas the chairman of the Joint Chiefs of Staff and the Director of National Intelligence will be allowed to participate only "where issues pertaining to their responsibilities and expertise are to be discussed."

"The appointment of Mr. Bannon is something which is a radical departure from any National Security Council in history," Republican Sen. John McCain, the chairman of the Senate Armed Services Committee, said on CBS' "Face the Nation" on Sunday.

"The one person who is indispensable would be the chairman of the Joint Chiefs of Staff, in my view," McCain added. "So it's of concern, this 'reorganization.'"

John Bellinger, an adjunct senior fellow in International and National Security Law at the Council on Foreign Relations and former legal adviser to the National Security Council, wrote on Saturday that the change was "unusual."

"In the Bush administration, Karl Rove would not attend NSC meetings," Bellinger said. "According to former Chief of Staff Josh Bolten, President Bush did not want to appear, especially to the military, to insert domestic politics into national security decision-making."

With his permanent seat at the NSC meetings, Bannon has been elevated above the director of the CIA, Mike Pompeo, who was not offered an open invitation.

"The CIA Director is typically invited to NSC and Principals Committee meetings," Bellinger said, though he added that President Barack Obama's list of invitees to such meetings did not include the CIA director.

Donald Trump's executive order on Saturday established Steve Bannon as a regular member of the National Security Council's Principals Committee. AP Photo/Gerald Herbert

CNN national security correspondent Jim Sciutto noted on Sunday that the move was "certainly unprecedented."

"You're putting in someone who is not Senate confirmed and taking out the Joint Chiefs of Staff and the Director of National Intelligence, who need to be Senate confirmed," Sciutto told CNN's Jake Tapper. "It raises questions about whose voices will be most prominent about key national-security decisions in the country."

Former Secretary of Defense Bob Gates told ABC on Sunday morning that sidelining the DNI and the chairman of the Joint Chiefs of Staff was "a big mistake."

"Adding people to the NSC never really bothers me," Gates said, referring to Bannon's new role on the committee. "My biggest concern is that, under law, there are only two statutory advisers to the National Security Council — the DNI and the chairman of the Joint Chiefs of Staff."

"Pushing them out," Gates said, was "a big mistake." He added: "They both bring perspective, judgment, and experience to bear that every president — whether they like it or not — finds useful."

A 'shadow National Security Council'

The Washington Post's Josh Rogin reported before Trump was sworn in that Bannon, Jared Kushner, and Reince Priebus comprised an informal "shadow national security council" that "sits atop the Trump transition team's executive committee and has the final say on national-security personnel appointments."

Kushner is Trump's son-in-law and senior adviser. Priebus is Trump's chief of staff.

"Bannon has been working on the long-term strategic vision that will shape the Trump administration's overall foreign-policy approach," Rogin reported, citing transition officials. He "is committed to working on the buildup of the military and is also interested in connecting the Trump apparatus to leaders of populist movements around the world, especially in Europe."

Before joining the Trump campaign, Bannon was the CEO of the far-right website Breitbart News — a website known for its antiestablishment, white-nationalist positions on issues such as immigration and trade. A week into his presidency, Trump has already prioritized numerous agenda items that reflect Bannon's nationalist views, including a border wall and a crackdown on immigration and refugee admissions. He also echoed Bannon's claim that "the media is the opposition party."

Breitbart's role inside the Trump White House is growing: Sebastian Gorka, an editor for national-security affairs at Breitbart who was paid by Trump's campaign for policy consulting, is expected to join the National Security Council. Julia Hahn, a hardline immigration writer for Breitbart, will join the administration as a special assistant to the president.

Trump with his daughter Tiffany and son-in-law Jared Kushner at a news conference at the Trump National Golf Club Westchester on June 7 in Briarcliff Manor, New York. Mary Altaffer/AP

The NSC Principals Committee will be chaired by retired Lt. Gen. Michael Flynn, Trump's national security adviser, and Tom Bossert, Trump's homeland security adviser. Defense Secretary James Mattis and Trump's secretary of state nominee, Rex Tillerson, have seats on the committee, but they "begin at a disadvantage," Rogin said.

They will be "fighting for influence in a team of strong personalities who are busily carving up issues, making plans and nurturing already close relationships" with Trump, Rogin wrote, referring to Bannon, Kushner, and Priebus.

The secretary of energy and director of the Office of Management and Budget were also removed from the committee's list of "regular members," and the deputy secretary of state will no longer be invited to every committee meeting. The chair of the Council of Economic Advisers will not be invited even "when issues to be discussed pertain to their responsibilities and expertise."

Unilateral moves

Trump already seems to be marginalizing the influence of career officials with extensive federal experience at the Department of Homeland Security, the State Department, the Department of Defense, and the Justice Department.

On Saturday, former Mayor Rudy Giuliani of New York City told Fox News that he helped draft Trump's "extreme vetting" executive order after Trump called him and asked how to do a "Muslim ban" "legally." Officials told CNN that the order was a unilateral move.

Department of Homeland Security staff, the officials said, were allowed to see the order barring refugees from the US only after Trump signed it, and National Security Council lawyers were prevented from evaluating it. The State Department and the DOD were also excluded from the process, NBC reported.

After seeing the order, the DHS interpreted it to mean that green-card holders from the banned countries — who have already been subjected to intense vetting — would be allowed to reenter the US from trips abroad. But that interpretation was overruled by the White House, which later said green-card holders would be allowed in only on a "case-by-case" basis.

Iraqi immigrant Hameed Darwish with Congresswoman Nydia Velazquez after being released at John F. Kennedy International Airport in Queens, New York, on Saturday. Andrew Kelly/Reuters

"The policy team at the White House developed the executive order on refugees and visas," CNN reported, "and largely avoided the traditional interagency process that would have allowed the Justice Department and homeland security agencies to provide operational guidance."

As a result, the order was imprecise and open to interpretation — and legal challenges.

The order "looks like what an intern came up with over a lunch hour," an immigration lawyer told Benjamin Wittes, the editor-in-chief of Lawfare and a senior fellow in governance studies at the Brookings Institution. "My take is that it is so poorly written that it's hard to tell the impact."

"The president has created a target-rich environment for litigation" with the order, Wittes wrote.

Lawyers and civil-rights organizations were already challenging the constitutionality of the ban hours after it was signed, arguing that the ban violated the Establishment Clause of the First Amendment by "explicitly disapproving of one religion and implicitly preferring others."

Lawyers representing two Iraqi refugees who were detained at John F. Kennedy airport in New York filed legal challenges to the order, and a federal judge in Brooklyn issued an emergency ruling Saturday evening to stay the continued deportation of travelers.

The ruling, a temporary emergency stay, now allows those who landed in the US and hold a valid visa to remain. Federal judges in Virginia, Massachusetts, and Washington also made emergency rulings on various aspects of the executive order.