A House panel on Wednesday subpoenaed the Department of Homeland Security for all documents pertaining to any suggestion by President Donald Trump that he would pardon immigration officials who broke the law to follow his orders to close the border, the first in a series of investigative moves Democrats are promising on the pardon controversy.

The House Judiciary Committee served the compulsory measure for all communications related to a pair of meetings Trump had earlier this year in which he reportedly floated those pardons. The committee is also asking for documents pertaining to any pardon promises for immigration officials or others engaged in trying to build Trump’s barrier at the U.S.-Mexico.

“The dangling of pardons by the president to encourage government officials to violate federal law would constitute another reported example of the president’s disregard for the rule of law,” said House Judiciary Chairman Jerrold Nadler, D-N.Y. “The Framers did not envision the use of the presidential pardon power to encourage criminal acts at the president’s direction.”

The news comes just days after The Washington Post reported that Trump is so eager to build hundreds of miles of border fence ahead of the 2020 election that he has directed aides to fast-track billions of dollars’ worth of construction contracts, aggressively seize private land and disregard environmental rules, according to current and former officials involved with the project.

He then told subordinates concerned about legal repercussions that he will pardon them of any potential wrongdoing should they have to break laws to follow his orders.

In response, the White House said Trump is joking when he makes such statements about pardons.

Earlier this year, The New York Times and CNN reported that Trump told acting Secretary Kevin McAleenan that he’d pardon him if he were jailed for denying entry to migrants seeking asylum.

The document requests, Democrats are promising, will be followed up with hearings as the party determines whether to impeach the president. Judiciary Democrats have discussed drafting articles of impeachment this fall and said in a release that Trump’s talk of pardons fits squarely into their inquiry into “abuse of power.”

“As the committee continues its investigation into whether to recommend articles of impeachment, it is imperative that we are able to obtain information about ongoing presidential misconduct and abuses of power,” Nadler said in the statement.