A declaration in the international system is one of the sources of international law (soft law, or lex feranda) comprising a set of certain political intentions and aspirations, and stating the willingness of its state parties to adhere to them in practice. This expression of will does not reflect the intention to create binding obligations. Therefore, a declaration is not subject to ratification by its parties, as are treaties or conventions.

 Although international declarations originally have no binding effect, they often reflect the rules and norms of customary law and could acquire legally binding effect as customary law through wide acceptance over time, as is the case of the Universal Declaration of Human Rights (1948). However, a declaration, by its nature, does not provide for a mechanism for enforcement, monitoring or evaluation of performance, as many modern treaties do.

In some cases, international political declarations could constitute a legally binding instrument if its parties express the corresponding obligation explicitly and in writing, or if the declaration is annexed to a treaty as an instrument that interprets or explains the treaty’s provisions. Such examples include unilateral declarations under the optional clauses of the Statute of the International Court of Justice on acceptance of its jurisdiction.

No declaration may contradict or infringe the over-riding principles or peremptory norms of international law.