The application of international law fulfills important task whereas enables the practical exercise of regulatory functions of its concrete rules in the international practice. In this respect it should be firstly noted that implementation of international law into domestic legal order is generally required by states as a necessary precondition for its application. Taking into account the absence of international rule prescribing specific form and manner of implementation, the relevant practice of the states is decisive. Within the states preferring the monist conception the direct application of international treaties (self executing treaties) is possible. Relevant provisions of the Vienna Convention on the Law of Treaties (1969) should be respected (namely Articles 25, 28, 29, 31) within the process of direct application of international treaties and their breach raises the international responsibility of states. The same requirement has to be complied with respect of application of international treaties by international organizations. There is no room for direct application of international treaties within states preferring dualist conception whereas the content of each treaty has to be obligatory transformed into specific kind of domestic legal regulation. Regarding the application of customary international law, the practice of states in principle confirms that they are not formally implemented into domestic legal orders of states and public bodies usually apply customary international law directly. The diversity of the judgments of international judicial bodies and decisions of international organizations prevent any attempt of states to apply them in a uniform manner. Similarly, as in the case of international treaties, there are no rules prescribing their specific application and different practice of states enjoy the leading role in the application of the international obligations arising from the international judgments and decisions.