The letter has exasperated Democratic lawmakers who had hoped to gather evidence and hear from witnesses, with the goal of voting on articles of impeachment by the end of the year.

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Some Democrats want to launch a counterattack against the White House’s resist-everything strategy. They’re lobbying to revive the “inherent contempt” process, which would allow Congress to arrest and fine or imprison officials who refuse to show up for their scheduled testimony. But at least so far, most Democrats want to just plow ahead with the impeachment investigation, interpreting the White House’s latest stiff-arm as an egregious example of obstruction of justice, bolstering their case for impeachment.

“The White House should be warned that continued efforts to hide the truth of the president’s abuse of power from the American people will be regarded as further evidence of obstruction,” Pelosi said in a statement released Tuesday. “Mr. President, you are not above the law. You will be held accountable.”

One way to get witnesses such as Sondland to testify is by holding them in inherent contempt. The procedure hasn’t been used since 1934, but some lawmakers believe that the time has come to reinstate the process, which would mean laying out guidelines for how to use it. “We need to revisit inherent contempt,” Representative Gerry Connolly of Virginia, a member of the House Oversight Committee, told me. “I can tell you the sentiment on [the] Oversight and Reform [Committee] is growing that we should do it.”

Representative Harley Rouda of California, another member of the Oversight Committee, told me that “there’s a lot more conversation around whether it should be used, and if so, how.” The defiance on the part of executive-branch officials shouldn’t go unanswered, Representative Jamie Raskin of Maryland told me. “It’s clear that the House should establish an inherent-contempt machinery and process,” he said.

But both Connolly and Raskin acknowledged that such a process would be time-consuming and impractical, given that there’s currently no set procedure for Congress to follow in fining or jailing officials who refuse to comply with subpoenas. And while none of the Democratic lawmakers I spoke with ruled out resorting to inherent contempt, it’s hardly the most appealing option for those already worried about the potential political ramifications of backing impeachment; after all, arresting noncompliant administration officials and throwing them in jail would arguably be a much more dramatic move than pursuing impeachment in the first place.

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“I just think that’s really unlikely. It’s kind of comic opera,” says Frank Bowman III, a law professor at the University of Missouri and the author of a recent book on impeachment. “What happens if you’re trying to arrest the vice president or the secretary of state? Those guys have got guys with guns. Do we have a showdown at the O. K. Corral over inherent contempt?”