Aparicio's firm, Aparicio, Arp & Associates LLC, has submitted petitions to the Inter-American Human Rights Commission representing, among others, the Cuban blogger Yoani Sánchez.
and the "Ladies in White" Group (Damas de Blanco).
More recently, he represented the French Maude Versini.He was the Ambassador of Bolivia to the United States (2002-2006) and was later President of the Inter-American Juridical Committee of the OAS.
Previously, he worked at the Organization of American States as Executive Secretary of the Summits of the Americas.
Before that, he was Under-Secretary of State for Foreign Affairs and Acting Secretary of State for Foreign Affairs of Bolivia.
Aparicio led several missions to the General Assembly of the United Nations, UNESCO and the Organization of American States.
He has also served abroad in Venezuela and France as Bolivia's Permanent Representative to UNESCO in Paris.In 2019, Aparicio sued President of Nicaragua Daniel Ortega at the Inter-American Commission on Human Rights (IACHR) after Ortega jumped a constitutional ban on presidential re-election with help from a Supreme Court filled with his supporters setting a major precedent for similar unconstitutional re-elections across the continent and more especially of his Bolivian counterpart Evo Morales.
Aparicio has become one of the most vocal opponents to dictatorships across Latin America, especially in Cuba, Bolivia, Venezuela and Nicaragua.