"voluntary" can also be pretty meaningless depending on the context. In the UK, if the police suspects you of shenanigans, they'll politely invite you for an "voluntary interview".
Of course you can decide to not go, it's voluntary, right? Yes, you can. Your choice. And when you reject their kind offer they'll come and arrest you so you can attend the interview.
Of course you can decide to not go, it's voluntary, right? Yes, you can. Your choice. And when you reject their kind offer they'll come and arrest you so you can attend the interview.