Last week, two men sporting yellow vests, toting a ladder, and driving around in a Mercedes removed about 15 works by the artist Invader from the streets of Paris. While one worked at removing the artist’s trademark mosaics based on the 8-bit graphics of the 1978 video game Space Invaders, the other ensured concerned passersby that they were working for city hall.

“They told me that the city had condemned Invader’s work after he’d installed a piece on Notre-Dame,” Pierre Ropert, a Parisian who saw the two vigilantes at work on August 2, claimed on Twitter. “This was false.” Now the municipal government is filing a formal complaint against the two men for impersonating city workers and stealing street art.

News of the thefts, which took place on August 2 and 3, spread quickly on social media, and pretty soon the mayor’s office was receiving tweets from angry citizens. “The city was interpolated on Twitter by Parisians who were asking themselves why city hall was removing the artist’s works,” a spokesperson for the city told AFP. “But we quickly realized that they were not our agents, our vehicles, or our vests.” Speaking with Libération, a spokesperson added: “And no, the city of Paris doesn’t provide its employees with Mercedes, yet.”

Among the works disappeared by the duplicitous duo are a large rendering of the Mona Lisa surreptitiously installed near the Louvre in 2014 and a mosaic of a character from the popular manga Dragon Ball. Another photo posted on Twitter shows one of the men in the process of removing a mosaic version of Mr. Potato Head.

“This ruins all my summers. Last year, I went a month without sleeping,” Invader told Libération, explaining that every August, when most French citizens go on vacation and Paris often feels empty, thieves target his works. “But things are accelerating now because they were caught in the act and photographed, and the reactions on social media show a heightened awareness among the public. I feel less alone.”

Though many were shocked at the string of brazen thefts, which took place in broad daylight, they are not exactly surprising. Invader’s auction record is a whopping $250,000, paid for a replica of a mosaic he installed on the street in Hong Kong, which sold at the local Sotheby’s auction house in 2015.

As his work has risen in value, Invader has adapted his materials to anticipate and deter thieves. “Nowadays, I use stronger glues and I have special tiles made that are more fragile and break when people try to remove them,” he told Libération. “But evidently, they’ve realized that the older pieces don’t stick as well because they’ve focused their efforts on those. They know what they’re doing, they’re professionalizing.”

Benjamin Sutton is an art critic, journalist, and curator who lives in Park Slope, Brooklyn. His articles on public art, artist documentaries, the tedium of art fairs, James Franco's obsession with Cindy...