Teams from the same conference shall not meet prior to the regional final if they played each other three or more times during the regular season and conference tournament.
Teams from the same conference shall not meet prior to the regional semifinals if they played each other twice during the regular season and conference tournament.
Teams from the same conference may play each other as early as the second round if they played no more than once during the regular season and conference tournament.
This is the rule from the NCAA. That being said these are shall nots, meaning it is permissable to have Iowa State and Houston meet in the elite 8 or regional finals. But the long standing practice is to avoid that as much as possible. So it's not against the rules but it is highly unlikely. In the scenario I was creating Marquette was 8th overall. ISU was in Detroit, Tennessee was in Dallas, and Arizona was in LA. That only leaves the East for Marquette. At this point they could seed Marquette there because they cannot go elsewhere. Move Marquette to the top three and slide the top three to the last two. Slide Arizona or Tennessee down and Marquette up. I am not sure which of these options they would choose.
All of that being said if Tennessee is the top 2 seed and we are next, they would take Detroit, our next location would be Dallas but the committee would likely look at Houston there and say okay we have two other sites, what's the next closest? Boston, okay ISU you are going to Boston.
This is the can of worms I was trying to avoid lol