The impeachment process is fundamentally unfair. Congress lacks authority to investigate the president. Witnesses should have executive branch lawyers.

White House attorneys are throwing out an array of arguments for keeping its officials from cooperating with the congressional impeachment inquiry. But legal experts say they are making a weak case.

Some even say the refusal to cooperate with the probe run by House Democrats could amount to obstruction that might itself become an article of impeachment against President Donald Trump.

"Not only can it be, it absolutely should be," said Heidi Kitrosser, a University of Minnesota constitutional law professor who has written about impeachment. "This is an effort to stymie Congress in one of its core roles."

The inquiry concerns whether the Trump administration sought to pressure Ukraine into investigating business done there by Hunter Biden, son of Democratic presidential candidate Joe Biden, and also probing whether Ukraine was involved in the 2016 U.S. election.

Four White House officials, including the top lawyer on the National Security Council, defied subpoenas from House investigators demanding they appear for depositions Monday.

Although the White House did not flatly assert executive privilege as the reason, it came extremely close, Kitrosser said.

"They are probably trying to have it both ways and trying to avoid the legal and political ramifications of claiming executive privilege while getting the advantage of it," she said.

Politically, an executive privilege claim could cross a line leading to more support for impeachment. Legally it's more or less the last attempt a president could make to prevent disclosure of evidence or testimony.

The NSC lawyer, John Eisenberg, is "absolutely immune" from congressional testimony as a senior adviser to the president, Eisenberg's attorney said in a letter. The letter involved separation of powers arguments in making that claim, contending his testimony is comparable to the president himself being forced before the inquiry.

Two other officials, Robert Blair and Michael Ellis, declined to testify unless they were allowed an executive branch lawyer present. The Justice Department issued a legal opinion Monday supporting that position, and the White House put out a statement.

"Democrats are just trying to force anyone, with any remote connection to this issue, to testify without administration lawyers present, and that puts national security at risk and also creates risks for potential witnesses who may unknowingly divulge privileged or classified information," White House spokesman Hogan Gidley said.

Democrats say there's no basis for ignoring their subpoenas. In a letter Sunday to Blair's attorney, the three committee chairs leading the impeachment probe said the claims have "no merit."

"Instead, it is the latest in a long line of baseless procedural challenges to the House of Representatives' authority to fulfill one of its most solemn responsibilities under the Constitution," they wrote.

Even if Trump were to overtly claim executive privilege, some experts say there's no constitutional provision that it would apply to impeachment.

"No communication involving the White House is subject to absolute immunity," said David Driesen, a Syracuse University law professor who has studied the issue. "No person is immunized from appearing by any claim of privilege known to the law."

This latest resistance to House subpoenas and testimony fits into the broader White House claim that the entire process is fundamentally unfair. Trump's lawyers have also made immunity claims in seeking to keep his tax records secret, but a New York court ruled Monday they can be released in a case likely to be settled by the U.S. Supreme Court.

In a recent letter to Democratic leaders, presidential counsel Pat Cipollone said Trump should have the kinds of due process rights typically found in court trials: the right to question witnesses, the right to see evidence, the right to cross-examine witnesses, and so forth. That position has been echoed by numerous Republican lawmakers.

"The president cannot allow your constitutionally illegitimate proceedings to distract him and those in the executive branch from their work on behalf of the American people," Cipollone wrote. "The president has a country to lead."

However, legal experts note that the Constitution and even prior impeachment proceedings do not lay out a roadmap for those kinds of rights in the initial House inquiry. Instead, that would come in a trial before the Senate, if it gets that far.

"The Constitution says virtually nothing about the procedures the House and Senate are to employ in carrying out their respective impeachment roles," wrote Georgia State University law professor Neil Kinkopf in recent article. "Indeed, the Constitution is completely silent regarding the procedures in the House."

Driesen said all of the efforts by the White House to slow down or halt the impeachment inquiry are just that - none have a basis in the law.

"Trump defies the Constitution and tries to distract from that fact by making baseless attacks. This is a good example," Driesen said.