Web crawlers can help photographers find copyright violations—but the bots are far from perfect, as a recent incident with former White House Photographer Pete Souza illustrates. Earlier this week, Souza shared a photograph that he took on Instagram, along with a story about how a photo agency was threatening legal action over the use of his own photo, which is part of the public domain.

Souza explained the story behind the image, a photograph of former president Barack Obama talking with Hillary Clinton aboard Air Force One. As an employee of the government, when Souza uploaded the photo to Flickr, it became part of the public domain. Fast forward a few years and in 2017, Souza includes the image in his portfolio on his work in the White House. Then, the photographer received an email from Copytrack on behalf of a photo agency, WENN Rights International, claiming that Souza was in violation of copyright law by sharing a photo that WENN held the copyright to. Souza says that he responded to the claim, only to be told that he was “legally obligated to compensate our customer for the damage caused by this copyright infringement.”

The story resulted in nearly 3,000 comments.

WENN CEO Lloyd Beiny later explained that the incident was an error. According to PetaPixel, the CEO explained that the photo agency also receives images from PR organizations to distribute to media outlets and that’s what he believes happened in the incident. He said that the matter was being dropped immediately.

[Read: U.S. Copyright Office Backing Photographer in Supreme Court Case]

The photo agency uses Copytrack, a program that helps photographers find copyright violations. The software uses bots to search the web for images similar to those registered.

Copyright law states that government work cannot be copyrighted; Souza’s White House work, as a contracted government employee, is part of the public domain.

Former White House photographer Souza isn’t the first to be threatened with legal action for using one of his own images that is registered to the public domain. Getty has been criticized for including public domain images in their paid library, resulting in lawsuits in 2019 and two in 2016. One of those lawsuits was a result of the photo agency sending Carol Highsmith a takedown notice for her own images that she had donated to the Library of Congress.