Neil Young is a longtime supporter of Bernie Sanders. Trump's use of song was not authorized.

[gratuitous]

8. His attorney will undoubtedly write a "cease-and-desist" letter

By this time, it's obvious that candidates need to get permission to use a song; there really isn't an "Oops, I did it again" freebie. That being said, candidates should be called out each and every time they steal someone else's creative output for their own aggrandizement. I'll make an immediate exception right here and now, though. Any reporter that wants to use the following question of my own creation can do so without limitation:

"Candidate X, I see that you're playing {insert name of stolen song here} by {artist's name here} at your {name of event here; e.g., announcement of candidacy, conviction for fraud, beginning of long prison sentence}. What else will you be stealing to further your campaign, and given your proclivity for theft, why should any voter seriously consider casting a ballot for a chiseler like you?"