Who owned the Mexican Flag?
And let's note that it wasn't in front of just any building.
From here, we have this: Scholes Hall
The administrative building for the University of New Mexico. The President of UNM, the Regents, and Provost, as well as many other top administrative positions have their offices here.
If you go to the link, there's what appears to be a nice Google maps satellite shot of the area. As you would guess from the description above, it's an extremely prominent public building.