WASHINGTON (Reuters) - Democratic U.S. lawmakers have vowed a court fight if necessary to secure the public release of Special Counsel Robert Mueller’s full report on his investigation into possible coordination between President Donald Trump’s 2016 campaign and Russia.

FILE PHOTO: William Barr testifies at a Senate Judiciary Committee hearing on his nomination to be attorney general of the United States on Capitol Hill in Washington, U.S., January 15, 2019. REUTERS/Yuri Gripas

But such a court challenge could face numerous hurdles, legal experts said on Monday, adding that the Justice Department might have reasons far beyond protecting President Donald Trump from legal and political fallout in withholding at least parts of the Mueller report.

“Congress can subpoena the information Mueller has collected, but faces huge hurdles in getting it,” said Ross Garber, a lawyer in Washington who focuses on political investigations. “It would have to file a civil lawsuit, which would take a long time to get through the court system, likely many years.”

Mueller is preparing the eagerly anticipated report on the investigation he took over in May 2017 examining potential Trump campaign conspiracy with Moscow to help tip the election his way and whether he has sought unlawfully to obstruct the probe.

A report finding either collusion or obstruction could lead the Democratic-controlled House of Representatives to consider launching the impeachment process set out under the U.S. Constitution to remove a president from office.

The Justice Department regulations governing Mueller’s appointment as special counsel called for him to write a “confidential report” explaining any criminal charges he brought, as well as any decisions not to prosecute. Mueller will submit his report to U.S. Attorney General William Barr, a Trump appointee who is required to provide a summary of Mueller’s findings to Congress.

Under the regulations, it is up to Barr to decide whether to release Mueller’s report to the public. House Intelligence Committee Chairman Adam Schiff said on Sunday his fellow Democrats would be prepared to subpoena the report to win its release, call Mueller to testify and take the fight to court if necessary.

If Barr defied a congressional subpoena and refused to disclose the full report, the House could vote to hold him in contempt of Congress and seek to enforce their subpoena through a civil lawsuit in federal court.

“The congressional subpoena power is an important fail-safe in case the Mueller report is suppressed or heavily redacted,” former federal prosecutor Elie Honig said.

“But it’s not as simple as, ‘Here’s a subpoena, hand over the entire report,’ or ‘Here’s a subpoena, now Mueller has to tell us everything he knows.’ There are various limitations on what a subpoena recipient can and would have to turn over, and some of those limitations could end up being litigated in court,” Honig added.

Such disputes between the Justice Department and Congress have happened before, typically being resolved through closed-door negotiations before a court has a chance to rule, University of Michigan-Dearborn political science professor Mitchel Sollenberger said.

In 2012, the House, then controlled by Republicans, voted to hold Democratic President Barack Obama’s attorney general, Eric Holder, in contempt for refusing to turn over documents related to a failed federal law enforcement operation dubbed “Fast and Furious” targeting gun traffickers.

A House committee sued Holder to obtain the documents. The litigation dragged on until a 2018 settlement was reached calling for the production of documents after Obama and Holder already had left office.

GRAND JURY DETAILS

One issue that could complicate Democratic efforts to win release of the report is that it might include information about closed-door grand jury proceedings that authorized Mueller’s indictments, Honig said. Barr has limits to his ability to make information about grand jury proceedings public, Honig added.

Another obstacle for securing release of the report is the possibility that Trump’s administration would invoke a doctrine called executive privilege that lets a president withhold certain information from Congress or the courts.

The U.S. Supreme Court has allowed use of executive privilege to ensure that a president can get candid advice from his advisers without worrying about the private conversations later being made public.

But the high court ruled in a 1974 case involving President Richard Nixon that executive privilege cannot be used to cover up White House wrongdoing. For that reason, Trump likely would not be able to invoke executive privilege to withhold the Mueller report, Sollenberger said. Nixon resigned later in 1974 amid the Watergate scandal.

In addition, the Justice Department has policies against it revealing information about ongoing criminal investigations and against releasing information about conduct it decides not to charge as criminal. While Mueller’s report would signal the end of his investigation, other federal prosecutors are pursuing related matters including the New York charges already brought against Trump’s former longtime personal lawyer Michael Cohen.

Barr himself criticized former FBI Director James Comey for revealing information publicly in 2016 about an investigation into Democratic presidential candidate Hillary Clinton’s use of a private email server while secretary of state.

“If you’re not going to indict someone, you don’t stand up there and unload negative information about the person,” Barr told his Senate confirmation hearing last month. “That’s not the way the department does business.”