The 1982 United Nations Convention on the Law of the Sea admitted legislation and enforcement jurisdiction carried out by the flag state. However, the emergence of substandard ships and the growing number of ship accidents at sea indicate that flag state jurisdiction is far from effective. Four aspects of these failures are examined in this paper. Confronted with the failure of flag state jurisdiction, port states have devised a subsidiary remedy to ensure their national interests and restore the effectiveness of flag state jurisdiction. A problem hereunder arises because non-explicit permission was given to port states to prosecute substandard ships. Thus, this paper further analyses four aspects of port state jurisdiction. The authors aim to analyse the failures and remedies associated with state jurisdiction over ships. It reviews the scope and deficiency of state jurisdiction in combatting substandard ships and illicit activities at sea. This paper also addresses the importance of port state control, regional memorandums of understanding and international conventions.

I. Introduction
II. Flag State Jurisdiction
    A. The Nature of Flag State Jurisdiction
    B. Flag State Jurisdiction in Progress
    C. The Scope of Flag State Jurisdiction in International Law
    D. Shortcomings of Flag State Jurisdiction
III. Port State Jurisdiction in International Law
    A. Port State Jurisdiction under Article 218 of the UNCLOS
    B. The Nature of MOUs in International Law: Treaties or SoftLaws?
IV. Enforcement of Port State Jurisdictionas a Subsidiary Remedy
    A. Port State Jurisdiction in Motion
    B. The Nature of Port State Jurisdiction: Territoriality orExtraterritoriality?
    C. The Role of Port State Jurisdiction as an Alternative Remedy
    D. Is Port State Jurisdiction a Sufficient Remedy?
V. Conclusion

• Jiancuo Qi(Ph.D. candidate at Korea University School of Law, B.A. (DMU), LL.M. (Swansea U.-UK)) Corresponding author
• Pengfei Zhang(Professor at Dalian Maritime University School of Law. B.A./LL.M (DMU), Ph.D. (Greenwich-UK))