If he has a musical composition license from a performing rights organization (PRO) such as ASCAP, BMI, and SESAC, they can complain all they want and he can still use it. The license can be obtained by either the campaign or the venue (e.g., hotel, restaurant, stadium). Venues usually pay periodic licenses to cover any performances of all the songs in a PRO’s catalog. So, if the campaign didn't have a license, but the venue had a license - and this song was in their catalog - he is free to use it.
Thanks. I was about to post the same question Rose did, but figured someone would ask first and also that some knowledgeable FReeper would answer.