I think you're asking about situations that involve "search and seizure" that are not directed by law enforcement. The trick is that such instances, though not undertaken by the police, often have legal implications.
- Public school authorities (mainly principals) are able to search students and their property under certain guidelines.
- People who work in a government office (a.k.a. public employee) can have their desks and file cabinets searched for evidence of misconduct.
- Employee drug testing is a form of search.
- Searches are permissible for inspections of property for code or health violations, such as restaurants and fire hazards.
- OSHA inspectors can search property, with some restriction, for safety violations.
- Welfare caseworkers have a system of "home visits," that while possible to deny, result in ramifications.