SMM3G, Iron Man and USPSA Nationals were all around four years ago and I dont think any one of them would really be considered to be natural terrain. Also, I think some might disagree with calling all three of them outlaw matches
Gose is right. I've been around a bit and the term "outlaw" was always to referred to a 3gun match that ran it's rules different than the old standby USPSA-ish rules set. Had nothing to do with terrain.