Paris MoU on Port State Control

The Paris Memorandum of Understanding on Port State Control is a regional agreement that coordinates the inspection of foreign ships in the ports of 28 European and North Atlantic maritime authorities. Signed in January 1982 and in operation since 1 July 1982, it functions through a risk-based inspection regime that assigns each vessel a Ship Risk Profile, determines how frequently that vessel must face inspection, and feeds a daily-updated targeting list to officer terminals across the member region. The Memorandum’s public performance lists, published each July, classify every flag state and every recognized organization (classification society) on a White, Grey, or Black scale based on three rolling years of detention data.

The Paris MoU covers waters from Iceland and Norway in the north to Portugal and the Adriatic in the south, and includes Canada as the sole non-European full member. Ships trading to any port within that region cannot avoid the regime: Montenegro’s accession on 1 July 2023 as the 28th member closed the last significant Adriatic gap, meaning that virtually any vessel delivering cargo to mainland Europe now falls within Paris MoU jurisdiction at some point in its trading pattern.

Origins and the road to 1982

Port state control existed in legal principle long before the Paris MoU gave it operational form. UNCLOS Article 219 authorizes port states to detain ships found not to meet applicable international standards and to prevent them from sailing until the deficiencies are corrected. The difficulty before 1978 was the absence of any mechanism that coordinated how different states exercised that authority.

The first attempt at coordination was the 1978 Hague Memorandum, a non-binding arrangement among Western European maritime administrations focused on enforcing seafarer living and working conditions under ILO Convention No. 147. The Hague Memorandum was still taking shape when, on 16 March 1978, the VLCC Amoco Cadiz ran aground off the coast of Brittany after a steering failure, spilling 223,000 tonnes of crude oil across 360 kilometres of French coastline. The grounding produced immediate political pressure. European transport ministers demanded a mechanism that went far beyond labour standards: one that would catch structurally deficient, poorly crewed, and inadequately equipped ships before they became casualties.

That pressure produced the Paris conference of January 1982. Fourteen European countries, Belgium, Denmark, Finland, France, Germany (then the Federal Republic), Ireland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, and the United Kingdom, signed the Memorandum of Understanding. Greece joined shortly after, bringing the founding group to fifteen. The MoU entered into operation on 1 July 1982.

The Memorandum has been amended repeatedly to incorporate new safety requirements as they emerged from the IMO. The sinking of the Herald of Free Enterprise in March 1987, which killed 193 people after the roll-on/roll-off ferry left Zeebrugge with its bow visor open, accelerated amendments related to ro-ro safety and ISM Code precursors. The 1993 SOLAS amendments requiring the International Safety Management Code, which became mandatory in phases from 1998, were incorporated into Paris MoU inspection standards as each phase entered force. Amendments addressing MARPOL Annex VI air pollution standards, the ISPS security code (post-2001), the Maritime Labour Convention 2006, and the Ballast Water Management Convention have each been absorbed in turn.

Membership expansion and Russia’s suspension

The original fourteen signatories grew steadily as the regime expanded eastward following the end of the Cold War and the accession of Central and Eastern European states to the European Union. Estonia, Latvia, and Lithuania joined after independence; Bulgaria, Croatia, Cyprus, Malta, and Romania acceded as EU membership extended; Iceland and Montenegro rounded out the European coverage.

Canada joined as the sole trans-Atlantic member, extending the coordinated regime to the North Atlantic approaches to European trade. Canada’s participation means that a vessel that has a poor inspection record in Le Havre faces consequences when it calls at Halifax, and vice versa.

Russia’s membership was suspended with immediate effect in March 2022 following Russia’s invasion of Ukraine. The suspension followed a letter from Ukraine’s Minister of Infrastructure requesting that the Paris MoU exclude the Russian Federation and cease recognizing certificates issued by the Russian maritime administration. The Russian Federation remains listed as a member in the formal 28-country membership count but exercises no voting rights, conducts no inspections, and has its ports excluded from the inspection network. At the time of writing the suspension had not been lifted.

Legal basis and governance

The Paris MoU is not an international treaty. It is a non-binding administrative arrangement among national maritime authorities. Its legal authority to detain ships flows from the domestic law of each member state, which in turn implements the powers granted to port states under UNCLOS and under the IMO conventions themselves. SOLAS Regulation I/19, MARPOL Articles 5 and 6, MLC Standard A5.2.1, and STCW Article X all contain explicit port state control provisions granting member states the right to inspect visiting foreign ships and to detain those found deficient. The Paris MoU harmonizes how those independently existing national powers are exercised, so that a ship cannot escape scrutiny by routing through a state with lax enforcement practices.

The executive body is the Port State Control Committee, composed of representatives of the 27 active participating maritime authorities plus a representative of the European Commission. The IMO and the ILO attend as observers. The Committee meets annually (the 58th meeting was held in Malmo, Sweden, in 2025) and deals with policy, finance, administration, and amendments to the inspection regime. Technical working groups handle specific subject areas between annual sessions.

The Secretariat is based in The Hague, the Netherlands, and sits under the responsibility of the Dutch Inspector General of Shipping. It organizes meetings, manages data exchanges, acts as the first point of contact for member states, and maintains the Memorandum text and its interpretive guidelines. Secretariat funding comes from the annual budget adopted by the Committee; member contributions are scaled to inspection volumes.

The conventions covered by inspection

An initial Paris MoU inspection checks certificates against the list in Annex 10 of the Memorandum text. That list covers the principal IMO instruments:

• SOLAS 1974 as amended, including all chapters on construction, stability, fire protection, lifesaving appliances, radio communications, safety of navigation, carriage of cargoes, dangerous goods, nuclear ships, high-speed craft, maritime safety measures, maritime security, bulk carriers, polar waters, and industrial personnel
• MARPOL 73/78 as amended, covering Annexes I through VI (oil, noxious liquid substances in bulk, harmful substances in packaged form, sewage, garbage, and air pollution)
• STCW 1978 as amended, including the Manila Amendments 2010
• The ISM Code (SOLAS Chapter IX)
• The ISPS Code (SOLAS Chapter XI-2 and the ISPS Code Part A)
• The Maritime Labour Convention 2006
• The International Load Lines Convention 1966 as modified by the 1988 Protocol
• COLREGS 1972 as amended
• The Tonnage Convention 1969
• The Ballast Water Management Convention 2004
• The Nairobi Wreck Removal Convention 2007

When certificates are valid on their face and the overall condition of the ship is satisfactory, the inspection ends. When clear grounds exist for believing the ship’s condition does not substantially meet requirements, the PSCO moves to a more detailed inspection. High-risk ships and ships of specific types above 12 years of age receive an expanded inspection regardless of initial appearance.

The New Inspection Regime

The Paris MoU’s current inspection logic is the New Inspection Regime (NIR), which took effect on 1 January 2011. It replaced the former quota-based system, under which each member state was required to inspect 25 percent of individual ships calling at its ports in a given year, with a risk-based regime that directs inspection effort toward the ships most likely to be deficient.

The NIR has two core components: the Ship Risk Profile and the selection scheme.

Ship Risk Profile

Every ship in the THETIS database carries a Ship Risk Profile (SRP) that classifies it as low risk, standard risk, or high risk. The SRP is recalculated overnight, every night, using two categories of parameters.

Generic parameters reflect the ship’s inherent characteristics: ship type, age, flag state (specifically, whether that flag appears on the White, Grey, or Black List), and the recognized organization (classification society) that issued the ship’s statutory certificates. A new vessel classed by a well-regarded RO and flying a White List flag starts from a relatively favorable position. An older vessel classed by a poorly performing RO and flying a Black List flag starts from an unfavorable one.

Historic parameters reflect the ship’s actual inspection record over the 36 months preceding the calculation: deficiencies recorded, detentions suffered, and the performance of other ships managed by the same ISM company. That last factor matters because PSCO experience shows that ISM management quality is ship-company-wide, not vessel-specific. A company whose fleet accumulates detentions pushes every ship in that fleet toward a higher risk score. Deficiencies recorded as accidental damage are excluded from the calculation.

The combination of these parameters produces one of three profiles:

Expanded inspections are also mandatory for any high-risk ship and for chemical tankers, gas carriers, oil tankers, bulk carriers, and passenger ships that are more than 12 years old, regardless of their SRP. The inspection clock resets after any periodic or additional inspection.

The practical consequence is direct. A ship with a clean record, a strong flag, and a well-performing class society can trade for two to three years without a Paris MoU inspection. The same vessel after two detentions, or after its flag state drops to the Black List, faces an inspection roughly every five months. Shipowners and managers have a measurable financial incentive to maintain the technical and operational standards that keep the SRP low.

Selection scheme

The selection scheme converts SRPs into Priority I and Priority II designations. A Priority I ship must be inspected because either its inspection window has closed or an overriding factor applies. Overriding factors that force an immediate Priority I inspection include: a specific report or complaint about the vessel from another authority, a pilot, or a port agent; a ship that has maneuvered in a manner creating a hazard; a vessel that has been involved in a collision or grounding; and a ship that has been refused clearance or reported by another member state.

A Priority II ship may be inspected at the port state’s discretion because it is within the inspection window but an unexpected factor, something indicating a potential threat to safety or the environment, has come to the PSCO’s attention.

Types of inspection

Initial inspection

Every ship subject to an inspection receives an initial inspection. The PSCO boards, checks the certificates and documents required by Annex 10, examines the overall condition of the vessel (bridge, accommodation, galley, engine room, cargo spaces, deck), and verifies that deficiencies from the previous inspection have been corrected. If everything is in order and there are no clear grounds for concern, the inspection ends with a clean report. Initial inspections of low-risk ships where the inspection window has just opened are designed to be brief precisely because the SRP system has already indicated the vessel is unlikely to be deficient.

More detailed inspection

When the initial inspection reveals clear grounds for concern, the PSCO conducts a more detailed inspection. Clear grounds include: a required certificate that is missing, invalid, or expired; evidence that the ship’s crew cannot perform basic operational drills; log books or records that appear falsified or incomplete; a report from a pilot or port agent alleging specific safety concerns; operational equipment found out of order; and failure to correct previously noted deficiencies. A more detailed inspection goes through the problem areas thoroughly and may cover random other sections of the ship as well. Human-element compliance under ILO, ISM, and STCW standards is examined.

Expanded inspection

High-risk ships and qualifying vessel types above 12 years of age receive an expanded inspection, which is the most intensive form. An expanded inspection covers the overall condition of the vessel including the human element, and then works through a list of type-specific risk areas drawn from Annex 8 of the Memorandum. For a bulk carrier, risk areas include structural integrity, hatch covers, and cargo hold condition. For a passenger ship, they include fire safety, stability, and evacuation systems. For a tanker, they include cargo system condition, inert-gas systems, and pollution-prevention equipment. The expanded inspection takes considerably longer than an initial check, often three to five hours on a large tanker or bulk carrier, and requires a PSCO trained for the specific ship type.

Deficiencies and detention

A deficiency is any finding where the ship, its equipment, its certificates, or its crew does not meet the requirements of an applicable convention. Deficiencies are recorded in the inspection report and loaded into THETIS. Minor deficiencies that can be corrected in port are noted and tracked. Deficiencies that pose a serious risk to the safety of the ship, its crew, or the environment, or that constitute a serious threat to the marine environment, are detainable deficiencies.

A detainable deficiency triggers a detention: the ship is formally prohibited from departing until the deficiency is corrected to the satisfaction of the detaining authority. Correction in port is the normal path. Where the deficiency cannot be corrected in the current port (for example, structural repairs requiring a drydock), the PSCO may authorize the ship to proceed to a nominated repair yard under conditions, such as limits on cargo to be loaded and requirements to keep specific systems operational.

Common detainable deficiency categories, by convention area, include: fire detection and extinction systems (SOLAS Chapter II-2), structural and machinery deficiencies (SOLAS Chapter II-1), lifesaving appliances (SOLAS Chapter III), ISM Code failures, STCW watch-keeping and certification violations, and MLC seafarer welfare provisions. The 2023 annual statistics showed SOLAS Chapter II-2 fire protection as the leading deficiency area by volume.

In 2023, the Paris MoU conducted 16,769 inspections of foreign ships. Of those, 639 resulted in detention, a detention rate of 3.81 percent. That figure was below the 4.25 percent rate recorded in 2022 but remained above the pre-pandemic rate of 2.98 percent recorded in 2019. The 2024 annual report (published June 2025) recorded a detention rate of 4.03 percent, an increase from 2023. Out of 16,769 inspections in 2023, 9,430 ships were found to carry at least one deficiency.

The White, Grey, and Black List

Every July, the Paris MoU publishes three flag-performance lists that quantify how well each flag state’s fleet performs during Paris MoU inspections. The lists cover any flag with at least 30 inspections in the rolling three-year period ending the previous 31 December. Flags with fewer inspections in that period are not scored and do not appear.

The scoring method uses the total number of inspections and detentions for the flag over the three-year window to calculate an Excess Factor: the ratio of actual detentions to the number that would be expected given the global average detention rate. A flag with an Excess Factor well below the global mean earns White List placement. Flags in the middle range land on the Grey List. Flags whose fleets are detained at rates well above the global mean appear on the Black List.

The lists valid for 1 July 2025 to 30 June 2026, based on 2024 inspection data, place 42 flags on the White List, 17 on the Grey List, and 12 on the Black List for the 2023 scoring year. These numbers shift annually as flag-state performance improves or deteriorates.

List placement has direct operational consequences for every ship flying that flag, through the generic parameter in the SRP calculation. A ship flying a Black List flag starts with a high-risk generic weighting, which pushes its SRP toward the high-risk category and shortens its inspection interval to 5 to 6 months, regardless of its own individual inspection history. Conversely, a vessel flying a White List flag that has also had clean inspections and is classed by a well-performing RO can qualify for a low-risk SRP and enjoy the 24 to 36 month inspection window.

The commercial pressure is real. Charterers and cargo interests increasingly use White List flag status as one criterion when selecting tonnage. Ports of call in northern Europe that handle high-value cargo where delays are costly have become sensitive to vessels arriving with known high-risk profiles. Flag state administrations with their fleets on the Black List face questions from shipowners about whether a change of flag would reduce operating costs through fewer inspections.

Recognized organization performance list

Classification societies authorized to issue statutory certificates on behalf of flag states on an IMO-recognized-organization basis appear on a separate Paris MoU RO performance list, also published annually in July. The methodology parallels the flag-state list: inspection and detention data for ships classed by each RO over a three-year rolling period determines a detention ratio, which classifies each RO as meeting or not meeting low-risk criteria.

For 2023, 32 recognized organizations appeared on the performance list. For 2024, 29 appeared. An RO in the lowest performance band adds to the high-risk generic parameter for any ship it classes: ships issued certificates by a poorly performing RO face higher SRPs and more frequent inspections.

The RO performance list is one of the mechanisms through which Paris MoU data flows back into the commercial market. A classification society whose ships are consistently detained faces questions from shipowners about whether class with that society increases operating costs. The major IACS member societies, including Lloyd’s Register, DNV, Bureau Veritas, ClassNK, and ABS, have historically maintained positions in the upper performance tiers. Non-IACS societies with smaller fleets show more variable results. See the articles on classification societies and the profiles of Bureau Veritas, DNV, and Lloyd’s Register for background on how RO authorization and oversight work.

Refusal of access

The Paris MoU’s most severe enforcement measure is the refusal of access: a formal ban preventing a ship from entering any port within the entire Paris MoU region. Banning is triggered by a pattern of repeated detentions:

• A ship flying a Black List flag is banned after three detentions within 36 months.
• A ship flying a Grey List flag is banned after three detentions within 24 months.
• A ship that jumps detention (departs a port where it has been detained without authorization) is banned immediately.
• A ship that refuses to proceed to a nominated repair yard after being authorized to leave under conditions is banned immediately.

Once a ban is imposed, the ship cannot enter any Paris MoU port or anchorage for a minimum period. A second ban following a first is longer. After a third refusal-of-access order, access is permanently refused to any port and anchorage in the Paris MoU region, with the sole exception of ports in the ship’s flag state. Three exceptions allow a port authority to grant access despite a ban: force majeure, overriding safety considerations, and the need to take on supplies or undertake repairs to put the ship into a safe condition, subject to adequate measures being in place.

Banning follows the individual ship’s IMO number, not its name, owner, or flag. A ship that changes hands, changes flag, and changes name while under a ban remains banned: the Paris MoU explicitly provides that such changes do not automatically revoke banning status. This prevents the evasion tactic of selling a repeatedly detained ship to avoid the ban.

In 2023, eleven banning orders were issued across the Paris MoU region. Individual banning announcements are published on the Paris MoU website with the vessel’s name, IMO number, and the port where the triggering detention occurred.

THETIS: the inspection database

The data that makes the NIR function is held in THETIS (Target-based Harbour Examination Through Information Systems), a database hosted and operated by the European Maritime Safety Agency (EMSA) from its headquarters in Lisbon. EMSA built and maintains THETIS under a service agreement with the European Commission; it is available to all Paris MoU member authorities.

THETIS receives port arrival notifications from the European Community Vessel Traffic Services and Information System (SafeSeaNet) in near real time. When a ship is expected at a Paris MoU port, THETIS already has its particulars, its recent inspection history from across the region, its current SRP, and the certificates last verified. The PSCO at that port logs into THETIS, sees whether the ship is Priority I or Priority II, and can call up the full inspection history before stepping aboard.

After each inspection, the PSCO enters the findings into THETIS: every deficiency with its convention reference and code, whether the deficiency was detainable, the action taken, and the outcome. That data feeds the overnight SRP recalculation for the ship and, in aggregate, feeds the quarterly performance statistics used to update flag-state and RO rankings.

THETIS is also used to enforce banning orders. When a banned ship enters a Paris MoU port, THETIS flags the entry to the local PSC authority.

Before THETIS, the Paris MoU used an older database called SIRENAC (Systeme d’Information Relatif aux Navires Controles), which was operated from Saint-Malo, France. The migration to THETIS, which went live in 2011 alongside the NIR, moved the database to EMSA and allowed for full integration with SafeSeaNet, which SIRENAC lacked.

Concentrated Inspection Campaigns

Each September through November, the Paris MoU runs a Concentrated Inspection Campaign (CIC): a focused, three-month exercise in which all member authorities apply a standardized additional checklist to ships they inspect during that period, on top of the normal inspection. The CIC topic is pre-announced well in advance, which creates an educational dimension: the announcement effectively puts the industry on notice that a particular compliance area will receive intensified scrutiny.

CICs are frequently conducted jointly with the Tokyo MoU, the regional equivalent covering the Asia-Pacific and covering roughly the other half of world seaborne trade by volume. A joint CIC means that the same targeted checklist is applied simultaneously in ports from Rotterdam to Yokohama, making it essentially impossible for a ship to avoid the campaign by trading between the two regions.

The history of CIC topics illustrates how the Paris MoU has used the campaign mechanism to respond to emerging compliance problems:

• 2025 (joint with Tokyo MoU): Ballast Water Management, covering the International Convention for the Control and Management of Ships’ Ballast Water and Sediments 2004
• 2024 (joint with Tokyo MoU): MLC 2006 seafarer wages and Seafarer Employment Agreements; 3,863 ships inspected across both MoUs during the campaign; 0.78 percent detained for CIC-related deficiencies
• 2023: Fire Safety Systems
• 2022: STCW standards and the Polar Code
• 2021: Stability in general
• 2019: Emergency systems and procedures
• 2018: MARPOL Annex VI air pollution compliance
• 2016: Maritime Labour Convention 2006
• 2015: Entry into enclosed spaces
• 2014: Hours of rest under STCW
• 2012: Fire safety systems
• 2008: SOLAS Chapter V safety of navigation
• 2007: ISM Code implementation
• 2006: MARPOL 73/78 Annex I oil pollution prevention
• 2002: ISM Code

The 2026 joint CIC is planned to focus on cargo securing, an area with persistent non-compliance that contributed to a number of container-ship fires and cargo-shift casualties over the 2020s.

Relationship with the Tokyo MoU and other regional agreements

Nine regional memoranda of understanding on port state control exist worldwide. The Paris MoU is the oldest. The Tokyo MoU covers 21 Asia-Pacific member authorities and conducts roughly 20,000 inspections per year, making it the largest single regional MoU by inspection volume. The two organizations maintain a close working relationship: joint CICs, shared data exchange protocols, and regular liaison between secretariats mean that Paris MoU detention data follows a ship when it trades in Tokyo MoU ports and vice versa.

The other regional MoUs cover the Indian Ocean (Indian Ocean MoU), the Caribbean (Caribbean MoU), the Mediterranean (Mediterranean MoU, operated separately from the Paris MoU), the Black Sea (Black Sea MoU), the Latin American coast (Vina del Mar Agreement), West and Central Africa (Abuja MoU), and the Persian Gulf (Riyadh MoU). Each operates its own database and issues its own detention orders, but all share data through the Global Integrated Shipping Information System (GISIS), the IMO’s central repository.

The United States does not participate in any MoU. The US Coast Guard operates its own port state control programme under 46 U.S.C. and 33 C.F.R. Part 160, conducting roughly 8,000 to 9,000 annual examinations through its National Maritime Center and Port State Control Program. USCG and Paris MoU do exchange detention data informally: a ship detained by Paris MoU for a serious deficiency will often receive heightened scrutiny when it next calls at a US port.

For the practical significance of the port state inspection encounter, see the article on port state control.

The ISM Code and the human element in Paris MoU inspections

The International Safety Management Code, made mandatory under SOLAS Chapter IX in phases from 1998, features prominently in Paris MoU inspections because it is the primary framework for checking whether a ship’s safety management system functions in practice, not just on paper. A PSCO can examine the safety management system during an expanded inspection: reviewing the SMS documentation, interviewing crew members about their understanding of muster duties and emergency procedures, checking that drills have been conducted at the required frequency, and verifying that non-conformities identified in internal audits have been corrected.

ISM deficiencies contributed 4.8 percent of all deficiencies recorded in Paris MoU inspections in 2023, according to the annual report. The ISM Code’s requirement that companies maintain a Document of Compliance (DOC) for the company and a Safety Management Certificate (SMC) for each ship means that an ISM deficiency during a Paris MoU inspection can have consequences at the company level, not just for the individual ship. See the ISM Code article for the full compliance framework.

MARPOL and environmental compliance

The Paris MoU’s reach into environmental compliance is most visible in MARPOL inspections. The six annexes of MARPOL cover oil, noxious liquid substances, harmful substances in packaged form, sewage, garbage, and air pollution. A standard initial inspection checks that an Oil Record Book (ORB) exists and shows plausible entries; an expanded inspection for a tanker will go into greater depth on the cargo system, the Oil Discharge Monitoring Equipment, and the Crude Oil Washing system where applicable.

MARPOL Annex VI air pollution compliance became a more active inspection area after the 0.50 percent global sulfur cap entered force on 1 January 2020. PSCOs at Paris MoU ports can verify the bunker delivery note (BDN) for the sulfur content of the fuel on board, check that compliant fuel is being used in sulfur emission control areas (SECAs, which cover the entirety of the North Sea and Baltic Sea), and examine the Fuel Oil Change-Over Log. Falsification of the ORB or BDN is itself a detainable deficiency. The 2018 CIC specifically targeted Annex VI compliance in anticipation of the 2020 cap.

For the full framework of air pollution requirements, see MARPOL Annex VI (once available); for oil pollution, see MARPOL Annex I.

MLC 2006 and seafarer welfare

The Maritime Labour Convention 2006 entered into force on 20 August 2013 and gave Paris MoU inspectors a consolidated set of standards for seafarer working and living conditions, replacing the patchwork of ILO conventions that preceded it. MLC Title 5 specifically addresses flag state and port state enforcement. Port states are authorized to inspect ships in their ports for MLC compliance, and the Paris MoU incorporated MLC into its standard inspection checklist from 2013.

The 2016 CIC targeted MLC compliance across the Paris MoU region and found the most common deficiencies in: crew accommodation and catering arrangements, hours-of-rest record-keeping, and financial security documentation for abandonment and personal injury. The 2024 joint CIC with the Tokyo MoU returned to MLC, this time narrowly focused on seafarer wages and the content of Seafarer Employment Agreements. Of 3,863 ships inspected across the campaign, 30 (0.78 percent) were detained for CIC-related MLC deficiencies. Deficiencies related to SEA content and wage documentation increased compared to the same period in 2023.

MLC compliance through the Paris MoU is one mechanism by which seafarer rights under the flag-state system are given practical enforcement teeth in port states that are parties to the MLC.

Overriding and unexpected inspection factors

The selection scheme distinguishes between overriding factors, which force an immediate Priority I inspection, and unexpected factors, which create grounds for a discretionary Priority II inspection. Understanding the difference matters for ship operators planning port calls in the Paris MoU region.

Overriding factors that require immediate inspection regardless of where the ship sits in its SRP inspection window include: a ship reported by a pilot or port authority as having deficiencies that pose a risk to safety or the environment; a ship involved in a collision, grounding, or stranding while on passage to port; a ship accused of a violation of discharge requirements under MARPOL; a ship that has maneuvered in a manner creating a hazard to others; a ship that has been denied clearance or has been the subject of a report from a master or seafarer; and a ship that cannot produce all required certificates in valid form.

Unexpected factors that may elevate a Priority II ship to inspection priority include: non-compliance with reporting requirements on arrival, inadequate or outdated charts, a change of owner or manager within the past three months, and a ship making its first call to a Paris MoU port. An operator who buys a ship whose previous flag’s administration appears on the Black List will often find that the combination of the new ownership flag, the old inspection history, and the “new management” unexpected factor places the vessel at the top of the targeting list for its first Paris MoU call.

Practical implications for shipowners and managers

The design of the NIR creates a clear hierarchy of compliance incentives. Ships that maintain strong inspection records under a White List flag and classed by a well-performing RO earn the 24 to 36 month low-risk inspection window. Ships that accumulate detentions or whose flag or class drops in the performance rankings face 5 to 6 month inspection intervals, which add real operating costs through inspection time in port and potential delays.

The ISM company link in the SRP calculation has a direct implication for fleet management: a series of detentions on one vessel within an ISM company can elevate the SRP of every other vessel under the same DOC. Managers with diverse fleets need to track inspection results across all vessels, not just the one currently in port. Companies that manage vessels for multiple owners under a single DOC face the same exposure: poor performance by one owner’s ship can affect the SRP of another owner’s vessel managed by the same company.

For vessels carrying hazardous or environmentally sensitive cargoes, the consequences of detention go beyond the delay itself. Charters with laycan windows, cargo delivery commitments, and port slot bookings can all be disrupted by even a one-day detention. A ship in the expanded-inspection category (high-risk or qualifying vessel type over 12 years old) needs to budget time accordingly when planning port calls in the Paris MoU region.

A ship under a banning order that enters a Paris MoU port will be identified immediately through THETIS. The ban is publicly listed on the Paris MoU website. The combination of public listing and the inability to trade within the Paris MoU region, which effectively covers all of Europe’s major ports, makes a third detention under the banning threshold an existential commercial event for a trading vessel.

Limitations

Several features of the Paris MoU regime deserve explicit acknowledgment by practitioners who rely on inspection data.

The inspection sample is not random. The SRP system directs inspection effort toward ships more likely to be deficient. This means the detained-ship statistics overrepresent the lower end of the fleet quality distribution: the 3.81 to 4.03 percent detention rate published in 2023 to 2024 reflects the detained proportion of inspected ships, not of all ships in the Paris MoU region. Well-maintained ships with low SRPs face inspection only every two to three years, and many of those inspections will produce no deficiencies. The aggregate detention rate is therefore a better indicator of the quality of the high-risk tail than of the fleet as a whole.

The White, Grey, and Black List covers only flags with at least 30 inspections over three years. Flags with smaller fleets in the Paris MoU region do not appear on the list and their SRP contribution falls back to a neutral default. Flags that strategically reduce their presence in Paris MoU waters to stay below the 30-inspection threshold would, in theory, escape the flag-state penalty, though such a reduction also reduces trading opportunities.

Detection varies by port and inspector. The Paris MoU harmonizes procedure but not detection ability. PSCO experience, training depth, and local port infrastructure differ across 28 administrations. A deficiency detectable in a busy northern-European port with well-equipped PSCOs may go unnoticed in a port where inspectors are stretched thinner. The Memorandum’s training committees and harmonization exercises address this gap but cannot fully eliminate it.

The regime applies only in port. A vessel at anchor outside territorial waters, or transiting without calling at a Paris MoU port, cannot be inspected under the Memorandum. Port state jurisdiction under UNCLOS Article 219 is inherently tied to the vessel’s physical presence in port. Flag state enforcement at sea is the parallel mechanism, and its effectiveness varies considerably across flag administrations.

Russia’s suspension creates a data gap. Russian vessels operating in the Paris MoU region continue to call at member-state ports, but inspection results for those vessels are no longer fed into a coordinated framework by a Russian PSC authority. The suspension also affects how Russian-flagged vessels are classified for SRP purposes, since the Russian flag administration is suspended rather than formally placed on the Black List.

The Memorandum is non-binding. It has no treaty-level enforcement mechanism. A member state that fails to conduct inspections, fails to upload results to THETIS, or releases a detained vessel early faces political pressure from other members, not a binding legal sanction. In practice, the regime has proven durable because member states have strong domestic legal obligations under the underlying conventions, and EU member states have additional obligations under EU maritime directives that give the NIR legal force within the EU.