In a lecture on law today I was told that in our state "assault" includes restricting someone's freedom - and freedom to move about as they please - effected by any methods of intimidation or fear.
I wonder how some 'religions' measure up on that one.
I think it was about "deprivation of liberty" where the intent is achieved by "a threat that detriment will be caused to the hostage if the demand is not complied with" - like a kidnapping - very stiff penalties.
It was a guest speaker. I won't be able to casually speak to that barrister about it. It's the Qld criminal code, but it's based on English law - you might be familiar with it.