Sorry, by "outside of the law" I meant apart from legally compelling someone. The word choice made it sound like I meant illegal methods. I meant volunteering information. I don't think people should ever do it. I've edited that in for clarity.

It's my personal opinion that the police should not even be allowed to request voluntary searches, but that's a different topic and one I recognize as more extremist. It's just too easy for requests to sound like demands in a society with manners. Phrases like "Would you please do X?" are often used for both optional things and required things because "Do X" sounds rude to people.