That's because criminal prosecution is limited to people who have a professional dependency on cooperation by LEOs.
Civil prosecution does not, and while individual officers may have qualified immunity, state/local government agencies, including police departments, have no legal privilege to disregard copyright.
If someone wants to film him, and then use the power of the Internet to amplify that video to be viewed by many, as is their current right, then they will simply have to do additional work to ensure they are not transmitting the officer's "tunes" to others. Take the time to edit the video provides a means to still publish. Not as easy as clicking submit, but still available as an option, without making a sensationalist claim that music is being "weaponized" by anyone.
People using straw man arguments to "weaponize" language and then place it online where it becomes divisive. That's more of a story than some dude using his phone in a clever way to protect from being video mobbed.
I am aware your comment may be sarcasm, so there's that.
A 16 year old working at McDonald's does not have the right to ignore the boss and play a gameboy (I was 16 in the 90's).
Banning music outside cop cars, or over the loud speaker, or on mobile devices while on duty does seem like something they definitely could do and would be within the law.
Suffice it to say, corporations are happy when the police find ways to let them exercise additional power that doesn't directly threaten their interests. What do they care if there's a fun song going on in the background if it lets police rough people up at their behest?
(For those who remember that Michael Jackson bought the Beatles catalog a few years ago and are wondering how McCartney has the rights, Jackson later sold it to Sony. When the songs became old enough, McCartney attempted to use the recapture provision of the Copyright Act of 1976 [1], 17 USC 203 [2]. Sony fought this, but in mid-2017 they settled and the rights went back to McCartney).
[1] https://www.legalzoom.com/articles/recapturing-copyrights-a-...
[1] https://liveforlivemusic.com/news/paul-mccartney-beatles-rig...
https://musicbusinessmadeeasy.com/understanding-the-music-sy...
I don't see an argument that cops shouldn't have to pay for things working in court.
But I can imagine that playing certain music for a large crowd requires a specific license? Something like a radio station?