According to E!, the photo agency Backgrid filed its lawsuit on Tuesday, October 29.
The lawsuit claims the 35-year-old violated federal law by posting the photo, and it also states that it had corresponded with the singer's reps about her "infringement" multiple times from 2017 to the beginning of this month, however that they failed to pay the agency to license the photo.
When Katy posted the pic, which shows her in a red suit and full prosthetics, and a pal dressed as Bill Clinton, she captioned it in her own sweet way.
"❤️BILL & HILL 4EVA❤️" she wrote at the time.
The court action against Katy follows a spate of prosecutions against other celebrities for posting images the themselves to Instagram that they don't own the rights to - because they haven't bought the pics.
While Ariana Grande and Justin Bieber settled the suits against them, Gigi Hadid's case was dismissed.