Sure it's legal, what do you think the paparazzi do their entire lives?
If you're in public, it is public.
Not true.
Paparazzi can film entertainers and such because these people are in the public eye. There's a different/higher standard for private citizens.
http://people.howstuffworks.com/paparazzi6.htm
Right of Privacy
The laws on the right of privacy vary from country to country. Under U.S. law, the right of privacy is defined by Black's Law Dictionary as:
1. The right to personal autonomy. The U.S. Constitution does not explicitly provide for a right of privacy or for a general right of personal autonomy, but the Supreme Court has repeatedly ruled that a right of personal autonomy is implied in the "zones of privacy" created by specific constitutional guarantees.
2. The right of a person and the person's property to be free from unwarranted public scrutiny or exposure. -- Also termed right to privacy.
So, if we are to understand that the law upholds our right to be "free from unwarranted public scrutiny or exposure," then it would seem paparazzi are not allowed to do what they do. There is, however, a loophole in the law. This loophole comes into the picture if you are legally defined as a
public figure.