You need to understand when you’re filming in sensitive and insensitive locations. Whether you realized it or not, if you’re filming from private property across the road, and filming someone incidentally, there are certain subjects that are off-limits specifically for security reasons. These areas include government buildings, some aspects of mass transportation like train stations, airports, and tunnels, and military installations. You should always search for signs that make it clear that the area prohibits recording devices or photography. Try to reach out to their media relations department before you arrive if you are unsure of whether your subject is off limits.
Does this apply to public figures? Not entirely. High-profile people such as politicians and celebrities endure less protection against being caught on film. This is because when a public figure is voluntarily in the public eye, to some extend they waive their privacy. That’s why the paparazzi’s footage of stars doing mundane things in life is an actual act that does not require a release form. This doesn’t mean that people do not have the right to control how you use their likeness. They can. You do not have the right to use the documentation with a commercial slant.