Author focuses on the law of the sea. According to international law warships and ships owned or operated by States used for non-commercial purposes enjoy immunity as regard to legal norms, execution and other jurisdictional measures of other states.
However, if the state conducts a commercial activity it ceases to act asa sovereign power and acts as a merchant and therefore cannot enjoy the immunity. When distinguishing the activities (functions) of state we speak about a restricted immunity, which was confirmed by long usage of States and expressed in customary and conventional international law.