A bombshell Washington Post report that revealed over the weekend that President Trump had seized interpreter notes from a private meeting with Russian President Vladimir Putin reignited Democrats’ desire to hear directly from an interpreter privy to those discussions.

“Every time Trump meets with Putin, the country is told nothing. America deserves the truth and the Foreign Affairs Committee will seek to get to the bottom of it. We will be holding hearings on the mysteries swirling around Trump’s bizarre relationship with Putin and his cronies, and how those dark dealings affect our national security,” Rep. Eliot L. Engel (D-N.Y.), the committee’s chairman, said in a statement.

House lawyers for the foreign affairs and the intelligence panels are reportedly meeting to determine what their options are to compel interpreters to testify before Congress about what transpired in a closed-door meeting between the two leaders, ABC News first reported.

But there has been trepidation about subpoenaing interpreters. Doing so raises a host of ethical and practical questions, and could open the door to abuses in future administrations and threaten diplomatic talks.

The issue first arose in July after Trump and Putin met privately in Helsinki with only one other person present, Marina Gross, a State Department interpreter. Accounts from the meeting varied, and at the time Democrats called for her to testify, but Republicans, then in control, didn’t entertain the idea.

Interpreters are intended to be impartial observers whose presence in private meetings is to facilitate conversation between people who don’t speak the same language. Confidentiality is a central tenet of their profession. Without it, principals in a meeting may not feel comfortable speaking freely, which undermines the purpose of a private meeting.

“Confidentiality is a cornerstone of all interpreter code of ethics, regardless of the setting. The parties we interpret for must be certain that we will not divulge what is being discussed and if they doubt this, they are not able to speak freely,” said Judy Jenner, a spokeswoman for the American Translators Association.

Moreover, she said, an interpreter’s notes are not intended to be transcripts or minutes, but rather guides for themselves, often written in symbols, so they are unlikely to give a full accounting of an exchange.

Rep. Bill Pascrell Jr. (D-N.J.) wrote a letter to House Oversight in July asking them to subpoena Gross. He acknowledged that it was “unprecedented” to subpoena a translator for details of a private meeting between a U.S. president and another world leader, but said, “Trump’s actions are unprecedented in a way that harms national security.”

“The American public deserves to know if the President made any further concessions, revealed national security secrets, or tried to profit off the presidency,” Pascrell wrote.

Around the same time, Rep. Adam B. Schiff (D-Calif.), now chairman of the Intelligence Committee, had filed a motion to subpoena Gross that was blocked by Republicans. On Sunday, after The Post’s report, he tweeted: “Last year, we sought to obtain the interpreter’s notes or testimony, from the private meeting between Trump and Putin. The Republicans on our committee voted us down. Will they join us now? Shouldn’t we find out whether our president is really putting ‘America first?’”

In response to the likely pushback if they move forward with subpoenaing the interpreters, Democrats will probably argue that Trump’s ties to Russia make this an extenuating circumstance. But there is valid concern that asking an interpreter to reveal what Trump and Putin spoke about when they met could set a precedent for lawmakers seeking details from any meeting between a U.S. president and an international official.

Complicating matters is the lack of documentation from those meetings. Trump’s seizure of notes from an interpreter occurred after he met with Putin in Hamburg in 2017, according to The Post’s reporting. If the translator for that meeting was to be subpoenaed, it would be their word against Trump’s, given that the president made sure there were no contemporaneous notes from the meeting.

But unlike in Helsinki, where it was just Trump and Putin and their interpreters in the room, other government officials were present for the Hamburg meeting and could corroborate the recollections of the interpreter, if it comes to that.

(This post has been updated.)