That's what I was thinking when I made my "eminent domain" comment. At what point can the government legally step in and say, "in the interest of the public welfare, we're going to let this happen?"

The government (most of them anyway) can do this almost immedeately as nearly all of them have some clause allowing action in the event of known criminal activity (whether they will after this goes through all the beaucracy is a different matter). The question with the parent is would private citizens be within their rights to do something like that. To that, the answer is, for the most part, no. I do not know of any countries (except palestine) which condone vigilantee justice.

Not quite. What you are referring to is vigilantee justice and most countries are not very fond of it (for good reason).