The "Happy" singer fired off a cease and desist letter to Trump, courtesy of his high-powered lawyer, Howard King.
"On the day of the mass murder of 11 human beings at the hands of a deranged 'nationalist,' you played his song 'Happy' to a crowd at a political event in Indiana," the letter begins. "There was nothing 'happy' about the tragedy inflicted upon our country on Saturday and no permission was granted for your use of this song for this purpose."
The letter continues, "Pharrell Williams is the owner of the copyright in "Happy," with the exclusive right to exploit same. Pharrell has not, and will not, grant you permission to publicly perform or otherwise broadcast or disseminate any of his music."
King goes on to say that using the song without permission "constitutes copyright infringement." He is asking Trump to cease and desist using the song going forward.
Pharrell is far from the first musician to be upset with Trump's song choices. Earlier this month, the estate for Prince took to social media to tell him to stop using "Purple Rain" at his events.