Williams issued a cease-and-desist for the use of his song, and condemned the choice to do so hours after 11 people were murdered at a Pittsburgh synagogue. Trump has repeatedly used songs without permission and received similar legal threats, including for songs by R.E.M., Aerosmith, Prince, Adele, and the Rolling Stones, among others.

Time – Pharrell Demands President Trump Stop Playing ‘Happy’ at His Political Rallies
BBC News – Pharrell orders Donald Trump to stop playing his music
Quartz – All the pop songs artists have asked Donald Trump not to use, in one playlist