In 2001, the Eastern Republic of Uruguay, an exporter of retreated tires, ignited the Mercosur´s Dispute Settlement Mechanism to challenge the Brazilian restrictive measures on the import of retreated tires. In 2006 another retreated tires exporter, the European Union, comes before the World Trade Organization – WTO – to challenge the Brasilia´s Policy and thus setting the first WTO case in which a developed country challenges an environmental measure taken by a developing country. What is the most remarkable in the present case, however, is how the Brazilian response to the complaints abruptly shifted from a mere juridical ground, within the Mercosur, into an environmental one, within the WTO. Why? At a first sight, the first reason that comes to mind to justify the Brazilian diplomatic contradiction is that, to the contrary of the WTO law, the Mercosur law did not offer a proper consideration to the environmental problematique. This is the hypothesis this paper intends to verify, always limited and driven by these two retreated tires cases.