The principle of freedom of association is contained in a number of international human rights instruments. In determining its objective and purpose，the Declaration of Philadelphia，adopted by ILO in 1944，addressed the freedom of association as a fundamental principle for the very existence of the organization. Article 20 of the Universal Declaration of Human Rights establishes that “［e］veryone has the right to freedom of peaceful assembly and association”. The 1966 International Covenant on Civil and Political Rights provides that “［e］veryone shall have the right to freedom of association with others，including the right to form and join trade unions for the protection of his interests”（article 22）. According to the International Covenant on Economic，Social and Cultural Rights adopted in the same year，“［t］he States Parties to the present Covenant undertake to ensure：（a）The right of everyone to form trade unions and join the trade union of his choice…”（article 8）. The 1969 American Convention on Human Rights stipulates that “［e］veryone has the right to associate freely for ideological，religious，political，economic，labor，social，cultural，sports，or other purposes”（article 16）. And Article 11 of the 1950 European Convention on Human Rights and Fundamental Freedom explicitly includes the right to form and join trade unions.