WASHINGTON — House Democrats sputtered with rage after President Trump vowed to fight “all” congressional subpoenas for witnesses and documents and accused his White House of a brazen pattern of obstruction.

But there might not be much they can actually do about it.

Even if the Democrats go to court to enforce their own subpoenas, they’d likely face a drawn-out legal battle that could result in a hollow victory, former Congressional staffers and experts on presidential investigations told VICE News. A court fight could grind on for months, or years, pushing into the 2020 campaign season or beyond. And Democrats will likely face obstacles from the Department of Justice, which ultimately would have to enforce any criminal contempt citations against the Trump administration's blanket refusal to comply with the House's requests.

“The across-the-board scope of this is, as far as I know, totally unprecedented,” said Richard Arenberg, who served on Capitol Hill for 34 years as a Senate staffer, including on the Senate Iran-Contra Committee. “I believe the Congress has the Constitution on their side, and in the end, they will prevail. But Trump may be able to just wait out the clock.”

Now, as the Trump administration digs in on disputes over Trump’s tax returns and sending former White House staffers to testify on Capitol Hill, the emerging political and legal war will test the true extent of Congress’s powers in the face of a defiant president.

“The across-the-board-scope of this is, as far as I know, totally unprecedented.”

Weapons of the weak

The House of Representatives has a relatively limited set of tools for enforcing compliance after a subpoena has been launched. The key enforcement power has long been considered to be a criminal contempt citation, which can result in prison for offenders.

Democrats entertained employing such powers earlier this week after Carl Kline, the former White House personnel security director, defied a Congressional subpoena by failing to appear at a hearing to discuss the Trump administration's issuance of security clearances despite allegations of big red flags on applicants’ resumes.

But if Democrats follow through with such a threat, they could run into a roadblock: The House must ask the president’s Department of Justice to enforce it.

And Trump’s DOJ might simply refuse.

Such a decision would find plenty of recent precedent, including in the Obama administration, which balked at a criminal contempt citation passed by the House against then-Attorney General Eric Holder.

At the time, Holder was holding back documents requested by House Republicans investigating Operation Fast and Furious, in a probe revolving around the allegation that weapons had been turned over to Mexican drug cartel leaders in a botched sting operation.

After two years of legal wrangling, a judge in D.C. eventually denied the House's attempt to have Holder personally held in civil contempt. That move could have meant a personal fine for Holder or even the possibility of jail — but the judge did order the DOJ to turn over some documents.

“The real concern for the House here is that there are all kinds of legal potholes that might end up knocking the case out of court.”

Democrats in Congress likewise voted to cite two top officials in the George W. Bush administration for contempt: Chief of Staff Joshua Bolten, and White House counsel Harriet Miers. Bush’s DOJ declined to enforce either, and after lengthy disputes in court, neither faced any direct penalty.

If the DOJ refuses to pursue any current or former Trump administration officials for criminal contempt of Congress, the House can still go for civil enforcement. But that approach could get tied up in court for months, or even years, pushing the resolution past the endgame of Trump’s first term, Arenberg said. He thinks delay may be part of Trump’s strategy.

“I think that’s part of the play here: The president feels he can slow-walk this, and take it all the way past the election,” Arenberg said.

The resulting legal back-and-forth would take at least a year to play out, and could easily stretch beyond the end of Trump’s first term, said Michael Stern, who served as senior counsel to the House of Representatives from 1996 to 2004.

“The real concern for the House here is that there are all kinds of legal potholes that might end up knocking the case out of court,” Stern told VICE News. “And if that doesn’t happen, it could just take a really, really long time.”

Congress = “paper tiger”

Even if Congress achieves a speedy win in court, that victory itself might even prove hollow, said Paul Rosenzweig, a former member of Ken Starr’s investigation into former president Bill Clinton and author of the lecture series “Investigating American Presidents.”

The Trump administration might, ultimately, take the position that it doesn’t have to comply with Congressional subpoenas, even after a judge has ruled that it has to, Rosenzweig said.

“I can see that happening, and I can see the Republican Party not caring,” Rosenzweig said.

Such a scenario, however unprecedented and remote, would kick off an outright Constitutional crisis over the question of how Congress and the courts would react to a presidential administration flagrantly defying both a Congressional subpoena and a court order saying it must be fulfilled.

“What happens if Donald Trump says, 'I’m not listening to the deep state courts!,’” Rosenzweig asked. “Is the [House] Sergeant-at-Arms going go get into a gunfight with the Secret Service on the White House lawn? I think not.”

“What happens if Donald Trump says 'I’m not listening to the deep state courts!’?”

The result, says Rosenzweig, is that a battle between Congress and the president may ultimately reveal Congress’ limited power to pry information out of the executive branch, unless Congress is willing to reach for the ultimate political weapon: impeachment.

In theory, impeachment could be used not just against the president but also against lesser members of the executive branch, such as Attorney General William Barr.

But given the Republican control of the Senate — and a two-thirds Senate vote necessary for impeachment to succeed — that prospect seems next to impossible.

“By and large, Trump is demonstrating, in his blunt and narcissistic way, that Congress’ investigative powers are really something of a paper tiger, unless both parties in both houses agree to reassert it,” Rosenzweig said.