As explained by the film's writer/director Álvaro Longoria (below) and narrator/co-producer Javier Bardem, the history of the place and people is pretty fascinating, involving as it does colonization by Spain, which eventually let the country go, after which incursions were made into it by Morocco, which were promptly rebuffed by the Sahrawi people (and their rag-tag army, the Polisario), but to little avail. Morocco, more powerful, continues to control the area.
Morocco appears to be taking its cues from the behavior of Israel, moving thousands of "settlers" into lands which originally belonged to the Sahrawi's. Unfortunately, because the Sahrawis were originally a nomadic people, big cities and permanent abodes were not something that developed in the Western Sahara. (The life-style of Nomads and Gypsies would seem to be something that the modern world will not or cannot countenance.)
Perhaps because the movie-makers did not get particularly up-close and personal with the Sahrawis themselves, much of the film is spent tagging along with Bardem and crew as they try to reach the Moroccans and question them about all this (as you might expect, this does not happen); going to the UN and making a short, impassioned speech; and speaking at length with France via one old fellow who makes pretty shameful, non-seeing excuses.
In addition to its showing as part of Spanish Cinema Now, Sons of the Clouds -- the title comes from the fact that, for centuries, this nomadic people followed the clouds that held the desert's most precious possession: water -- is available now on DVD and from all major Digital Outlets via GoDigital -- including iTunes and Vimeo -- for download sale and/or rental.