Declarations made by way of unilateral acts, concerning legal or factual situations may have the effect of creating legal obligations. An undertaking of this kind if given publicity, and with the intend to be bound, even though not made in the context of international negotiations is binding. Nothing in the nature of quid pro quo nor any subsequent acceptance, not even a reply or reaction from other states is required for the declaration to take effect.
Not all unilateral acts imply obligations; the intention has to be ascertained by interpretation of the act. When states make statements by which their freedom of action is limited, a restrictive interpretation is called for.
With regard to form IL does not imposes any requirement
A basic principle governing creation and performance of legal obligations, whatever their source, is good faith. Trust and confidence are inherent in international co-operation