Bryan,
You write that this man is a "public figure." Do you mean that he is a politician or a member of a local/national government? I'm just trying to figure out what you mean by "public."
By definition, if a given person is a public figure and they have agreed to an interview, everything they say is on the record and can be used.
In most countries, the only restriction that I can think of would be filming someone inside their homes without consent.
