PHILADELPHIA (AP) — A federal judge warned Justice Department lawyers on Friday that they were making “dangerous” and “horrifying” statements when they said the Trump Administration can decide what part of American history to display at National Park Service sites.

The sharp exchange erupted during a hearing in Philadelphia over the abrupt removal of an exhibit on the history of slavery at the site of the former President’s House on Independence Mall.

The city, which worked in tandem with the park service on the exhibit two decades ago, was stunned to find workers this month using crowbars to remove outdoor plaques, panels and other materials that told the stories of the nine people who had been enslaved there. Some of the history had only been unearthed in the past quarter-century.

“You can’t erase history once you’ve learned it. It doesn’t work that way,” said Senior U.S. District Judge Cynthia Rufe, an appointee of President George W. Bush.

The removal followed President Donald Trump’s executive order “restoring truth and sanity to American history” at the nation’s museums, parks and landmarks. In Philadelphia, the materials were put in a pickup truck and then into storage, leading Rufe to voice concerns about whether they were damaged.