Abstract
The Southern Common Market (Mercosur) is a regional political and economic bloc comprising certain South American countries. The main objectives of Mercosur include sustainable development, harmonising legislation in relevant areas to strengthen the integration process, identifying investment opportunities, and promoting the growth of domestic and regional markets. As such, there is a need for clear rules and principles of private international law within the Mercosur Member States. Certainty regarding private international law rules will contribute to sustainable development and strengthening economic growth in the Mercosur region. This article examines the rules and principles of choice of law, which is paramount in international commercial contracts. More specifically, the article focuses on the issues related to determining the existence of a tacit choice of law in international commercial contracts in Argentina, Brazil, Paraguay and Uruguay. For each country, the article analyses the level of strictness of the criteria for inferring a tacit choice of law, the indicators that have been relied upon, and the weight that has been attached to these factors.