Spain joined the UN in 1955, and the UN's main bodies pressured Spain to proceed with the decolonization of "Spanish Sahara," which shortly after, and under the name of Western Sahara, was included in the list of non-self-governing territories. When Spain was preparing the referendum of self-determination in 1975, the UN General Assembly asked for it to be suspended until the International Court of Justice issued an advisory opinion. This opinion established that, in 1884, there were no ties of sovereignty between Morocco and Mauritania and the people of the territory, and that the conflict should be resolved through the exercise of the right of self-determination. Nevertheless, following the signing of the Madrid Agreements and the withdrawal of Spain from the territory, Morocco and Mauritania occupied it, forcing the Saharawi people to start a war of national liberation that would last until 1991. That year launched a peace plan negotiated by Morocco and the POLISARIO Front, which provided for the holding of the referendum on self-determination. When the UN's Mission for the Referendum in Western Sahara issued the composition of the census in 2000, Morocco decided to abandon the peace plan, accusing the UN of bias, thus leaving the conflict in an apparent impasse. Since 1975, the result of this conflict has seen the Saharawi people split between those who survive through international humanitarian aid in refugee camps in Tinduf, Algeria, and those who live in their own country under Moroccan occupation. This book explains the key issues of the conflict, from the perspective of international law, with particular emphasis on the development of the peace plan, as well as the causes and consequences of its paralysis.