For example, a buddy of mine recorded or captured a photo/video of someone let us say fighting or just talking in a public place such as the public road. It is legal to post it in social media even though that buddy of mine has no permission from the subjects in the photo/video?
- The photographer owns the copyright.
- The subject has no right not to be photographed: in [R v Sotheren (2001) NSWSC 204] Justice Dowd said “A person, in our society, does not have a right not to be photographed.”
- Australia has no privacy rights on person-to-person interactions (and pretty trivial ones on person-to-business).
There are limitations mainly related to voyeurism and commercial use, which are discussed at http://www.4020.net.
Depends on the jurisdiction, of course. In many parts of Europe, the answer is "probably not."
- A picture of the public road with people in the background (freedom of panorama) is different from a picture of people who happen to be on the public road. If the picture is about "people fighting," they are probably not the background.
- People fighting may or may not constitute a newsworthy event, which means freedom of the press intersects with privacy and copyright laws.
- Picturing the victim of a crime that way might even get you into jail.
How the various rights balance (your right to report a fight, their right to control their own picture) depends on the country.