The work focuses on the analysis of the process of democratisation, starting from the illustration of the principles of self-determination and democracy and their sources, and ending with two cases studies: The Libyan and the Haitian situations. The work begins with the Tom Franck's article entitled "The Emerging Right to Democratic Governance", published in 1992 in the American Journal of International Law, as it has initiated an important debate on the relationship between international law and democracy. The author analyses how, in occasion of the attempted coup in Russia and of the successful overthrow of elected president Jean-Bertrand Aristide in Haiti, respectively in August and September 1991, international organizations gave an unprecedented response. In both cases "the leaders of states constituting the international community vigorously asserted that only democracy validates governance." Furthermore, Franck claimed either that legitimacy of governments was no longer a matter of national arrangements, but of international law or that democratic governance was becoming an enforceable entitlement. Hence, this study is aiming to examine the three 'building blocks' identified by Franck as fundamental features of democracy, that is to say, the principle of self-determination, the right to 'free political expression' and the right to 'free and fair periodic elections'. The right of self-determination is mentioned in the United Nations Charter in Article 1 (2), a programmatic rule which refers to self-determination as a 'purpose' on the United Nations. Being friendly relations among nations one of the core purposes of the United Nations, they should find their legitimacy, according to the Charter, in respecting equal rights and self-determination of peoples. Besides the analysis of all the aspects that identify this principle as fundamental in international law, the major aim of this study is to examine the United Nations' politic in guaranteeing self-determination as a collective right through decolonization, in the light of the two Human Rights Covenants of 1966 and in view of article 55 of the United Nations Charter, a declaratory norm which gives some hints concerning the operational measures to be taken by the UN in order to give more substance to the purpose of peaceful and friendly relations among nations 'based on respect for the principle of equal rights and self-determination of peoples.' Moreover, for what concerns the principle of democracy, the work has set itself the aim to scrutinize its vagueness, as the Vienna declaration and the Agenda for Peace of the United Nations Secretary General only refer to the positive effects of democracy on human rights, development and peace without giving any specific definition of the term. Nevertheless, according to the United Nations General Assembly resolution adopted in 2000 under the title "Promoting and Consolidating Democracy", democracy is characterised by pluralism, the protection of human rights, separation of powers, rule of law, elections, development of a civil society, good governance, sustainable development, solidarity, and social cohesion. Furthermore, the United Nations works incessantly for promoting human rights, development, as well as peace and security, assisting parliaments to enhance the checks and balances that allow democracy to thrive, giving assistance to develop policies and legislation in order to guarantee the rights of freedom of association and expression, and, last but not least, providing electoral assistance and long-term support for electoral management bodies. In that regard, the work's purpose is to scrutinize the situation in Haiti and the United Nations' intervention, which can be considered the most purposeful moment of United Nations' activity in favour of democratic regimes.