In this edition of Countdown, we explore how the global enforcement regime in shipping can be applied to the International Maritime Organization Net-Zero Framework (IMO NZF). We offer insights into the enforcement mechanisms that will underpin its implementation, highlighting both the established elements and those still requiring further clarification. 

• The IMO NZF is backed by a well-established enforcement regime, strengthening confidence in compliance.  

• Enforcement of the IMO NZF is multi-layered, involving flag States, Port State Control, recognized organizations, and the IMO Member State audits, with overlapping enforcement roles. 

• Industry mechanisms can further incentivize compliance including contractual obligations in charterparty agreements, vetting tools, and insurance clauses tied to compliance.

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Enforcement is the backbone of credible regulation. As the IMO NZF moves from policy to practice, consistent enforcement is essential to protect compliant investments and uphold market fairness. 

The IMO is responsible for developing and adopting the regulations that govern global shipping; however, it does not oversee their enforcement. National authorities are responsible for enforcing IMO regulations – often through regional cooperation. 

In addition to the ship-based enforcement covered here, it will be equally important to ensure that sustainable maritime fuels have been produced, distributed, transported, and bunkered in a manner that lives up to what they claim. We will go into further details about this in an upcoming edition.

The world’s commercial shipping industry operates under a comprehensive set of legally binding international conventions like the SOLAS (Safety of Life at Sea) and the MARPOL (Prevention of Pollution from Shipping) that govern maritime safety, environmental protection, and seafarers’ rights and welfare.  

The United Nations Convention on the Law of the Sea (UNCLOS) provides the overarching legal framework for maritime governance. It establishes the mandate under which the IMO and other maritime conventions are implemented and enforced. 

Under these conventions, the flag States hold primary responsibility for ensuring that ships flying their flag comply fully with international standards. To complement flag State enforcement, a global system of Port State Control (PSC) has been established. PSC enables the port States to inspect foreign ships visiting their ports to verify compliance with international regulations.  

Figure 1: An overview of the actors involved in regulatory enforcement within international shipping.

Together, the flag States and Port State Control form a double-layered enforcement mechanism that upholds the integrity of international maritime law and promotes safe, secure, and sustainable shipping worldwide. 

Flag States delegate statutory certification and verification tasks to recognized organizations (ROs), which support the implementation of IMO regulations. The mechanism is further strengthened by mandatory IMO Member State Audits. These actors collectively oversee compliance across the global fleet.  

In the following segment, we break down how these enforcement mechanisms work and outline their potential role in ensuring the success of the NZF.  

The term “flag State” originates from the historical practice of ships flying flags as a symbol of their affiliation with a particular nation. Over time, these flags evolved into official and powerful symbols of statehood, serving as visible evidence of the nationality of a ship’s registration.  

Today, for a country to be recognized as a flag State, it must have the necessary financial and technical resources commensurate with the size and type of its fleet and adhere to all the norms and regulations established by the IMO.  

Not all flag States have the necessary infrastructure and required technical, human, or financial resources to fulfil all their obligations under IMO conventions. To bridge these capacity gaps, the flag States commonly delegate certain statutory functions to classification societies, identified as ROs under various IMO conventions and frameworks, which will include the IMO NZF.  

Recognizing the need for delegation of responsibilities by flag states, the IMO has established the IMO RO Code. This code provides a framework for flag States to authorize and oversee their authorized ROs, ensuring that minimum uniform standards are maintained in areas such as safety, security, and environmental protection. The Code also outlines the responsibilities of both flag States and ROs, promoting transparency and accountability in delegated functions. 

When a government accepts an IMO convention, it implicitly agrees to incorporate its provisions into national legislation and to implement and enforce them effectively (see previous newsletter on the IMO process). As part of this commitment, all IMO member states are subject to the IMO Member State Audit Scheme (IMSAS), a mandatory mechanism designed to assess how well member states comply with their obligations under applicable IMO instruments, in accordance with the provisions of the IMO Instruments Implementation Code (‘the III Code’). 

The audit scheme plays a critical role in promoting transparency, accountability, and continuous improvement in maritime governance. It evaluates the extent to which member states: 

• Fulfil their responsibilities as flag, port, and coastal states. 

• Maintain effective legal, administrative, and enforcement frameworks. 

• Implement and enforce IMO conventions consistently and effectively. 

PSC serves as a vital second line of enforcement, complementing flag State measures. While flag States are primarily responsible for the ships registered under their flag, port States play a key role in verifying that all ships including foreign flagged ships calling their ports meet the international standards (See UNCLOS, Art. 217, 218 & 219).  

Through inspections, PSC acts as a safety net, identifying deficiencies in ships that may not fully adhere to conventions such as the MARPOL and SOLAS. These inspections help prevent substandard ships from operating, contributing to global maritime safety, environmental protection, and fair competition.  

The critical function of PSC is its authority to impose the ultimate sanction: detaining a ship in port if it is deemed to pose an unacceptable risk to safety or the marine environment. Ship operators strive to comply with applicable regulations to avoid detention, which carries significant reputational and financial consequences, including lost time in service. 

PSC operates under a framework of regional cooperation, formalized by the IMO Resolution A.682(17). Currently, nine regional agreements coordinate PSC activities across different parts of the world, as illustrated in the map below.  

The United States Coast Guard maintains an independent PSC regime, aligned with the IMO standards but operating outside the regional MoU structure.

Figure 2: World map depicting the nine Memorandums of Understanding (MoUs) on Port State Control. The United States Coast Guard maintains its own regime. The Russian Federation is also a member of Paris MoU but currently suspended.

The MoUs coordinate efforts to maximize ship coverage, enabling authorities to share information on high-risk vessels and ensure those vessels are prioritized for inspection. The MoUs also cooperate through a shared risk profile of flag States, based on inspection outcomes and the number of detentions issued against vessels registered under each flag.  

This globally coordinated system ensures that ships are subject to consistent scrutiny regardless of where they operate. This consistency strengthens the implementation of IMO conventions, and supports safer, cleaner, and more transparent maritime operations.

The approved text of the IMO NZF does not explicitly state that failing to present a valid Statement of Compliance is a detainable deficiency. However, the framework does amend the MARPOL Annex VI (Regulation 10) to bring the NZF Statement of Compliance and annual compliance statements within the scope of PSC enforcement. 

The Workplan following IMO NZF adoption includes a review of PSC procedures (Resolution A.1185(33)). When these procedures were previously updated for the IMO Data Collection System (DCS) and the Carbon Intensity Indicator (CII), their respective Statements of Compliance were added under the chapter on “Detainable deficiencies” (see Appendix 18, Para 2.7.2.3 in the Resolution). It’s therefore expected that the IMO NZF Statement of Compliance will be included in the same way.  

This question will be central to the development of the role of PSC in enforcing the IMO NZF. Even though the existing IMO PSC procedures provide that the absence of required certificates may justify detention, they also acknowledge that ships from non-party States are not obligated to carry such certificates. Nonetheless, under the principle of no more favorable treatment, substantial compliance is expected before a ship is allowed to sail. 

Substantial compliance would require that the ship meets the intent of the regulation even if minor deficiencies exist. Although defining substantial compliance under the NZF is complex and warrants a detailed analysis, it is safe to assume that proving it would be challenging in the absence of a Statement of Compliance.  

As for other enforcement actions, such as criminal prosecution, fines, or sanctions against crew or ship management, these will depend on how individual member states choose to implement and enforce the IMO NZF.  

Insights can be drawn from the enforcement of the IMO Sulphur Cap introduced in 2020, where violations led to: 

• vessel detentions, 

• fines imposed on shipowners and masters, 

• criminal penalties, including imprisonment of up to six years, and 

• bans on non-compliant ships and crew. 

These precedents suggest that serious breaches of the IMO NZF requirements, especially deliberate non-compliance, could attract similarly stringent penalties from PSC.

The shipping industry itself will play a critical role in the enforcement of the IMO NZF. While regulatory compliance is mandatory, many operators are expected to accelerate compliance efforts voluntarily, driven by commercial incentives, reputational considerations, and the desire to avoid penalties or detention due to non-compliance.  

Commercial contracts and charterparty agreements will serve as informal enforcement mechanisms, embedding NZF-related obligations into business practices. Charterers and cargo owners are increasingly factoring environmental performance into vessel selection, making compliance a competitive advantage. 

In addition to contractual enforcement, industry-led self-regulatory programs have proven effective in raising safety and compliance standards across the industry. These include Ship Inspection Report Programme (SIRE), RightShip and Common Marine Inspection Document (CMID). 

These programs operate through partnerships between industry stakeholders, offering inspection reports and vetting tools that are routinely consulted by charterers worldwide. They have evolved to include checks under the MARPOL Annex VI and are expected to promptly adapt to the requirements of the NZF. 

Finally, marine insurance policies often include clauses requiring compliance with international standards. A ship without a Statement of Compliance may be deemed higher risk, leading to higher premiums, limited coverage, or exclusion from certain underwriting pools.  

These market-based incentives will complement regulatory enforcement helping to drive higher levels of compliance and transparency across the global fleet of the relevant ship types. 

The successful implementation of the IMO NZF will depend not only on the robustness of its regulatory design but also on the clarity and effectiveness of its enforcement mechanisms. 

By ascribing responsibilities across flag States, recognized organizations, and PSC authorities, the NZF establishes a multi-layered compliance architecture that reflects the complexity of global shipping operations and increases the likelihood of achieving high rates of compliance. 

Market-based mechanisms and self-regulatory initiatives will play a complementary role, reinforcing compliance, increasing accountability, and accelerating the sector’s transition to net-zero emissions. 

However, the framework also introduces new contractual, operational, and legal challenges that must be addressed to ensure consistent and equitable enforcement. As the industry adapts to these evolving requirements, collaboration between regulators, industry stakeholders, and enforcement bodies will underpin the industry’s ability to adapt.

Authors: Jyotsna Dargan (seconded to MMMCZCS) and Pernille Palmelund Sørensen (MMMCZCS)