Forbidden zones

[Argon]

Fairly self explanatory, simply zones colonists don't wander into unless broken, or ordered specifically to do so. This would be endlessly helpful.

-Argon

[b0rsuk]

What for ?
The only use I can think of is when there's a siege. And if you wanted to designate a forbidden zone each time there's enemy at the gates, there must be a better way to do this. Removing the zone after all are killed would get old fast.