The Paris MoU covers Port State Control in Europe and the North Atlantic; the Tokyo MoU covers the Asia-Pacific. Both enforce the same IMO conventions and both class ships by risk, but the scoring thresholds, inspection windows, flag lists and enforcement tools differ enough that a fleet trading both regions carries two separate risk profiles.
What is the core difference between the two MoUs?
Legally, very little: both are regional agreements among maritime authorities to inspect foreign ships against SOLAS, MARPOL, STCW, MLC and the other instruments, and a deficiency is a deficiency in either region. The core difference is enforcement posture. The Paris MoU is backed by EU law (Directive 2009/16/EC mirrors its regime for EU member states) and carries a formal refusal-of-access mechanism that can shut a ship out of the entire region. The Tokyo MoU relies on inspection pressure instead: shorter windows, a published list of under-performing ships, and member authorities alerted to board them at every opportunity.
For a fleet manager the practical difference is rhythm. In the Paris region a standard risk ship might see PSC once a year. In the Tokyo region the same ship is due every 5 to 8 months, so the Asia-Pacific trade simply generates more boardings per ship-year, even for decent performers.
Do they use the same ship risk scoring?
No. The Tokyo MoU's New Inspection Regime (NIR) was modelled on the Paris system, and both sort ships into high, standard and low risk. But the parameters diverge in ways that change real outcomes:
| Paris MoU | Tokyo MoU | |
|---|---|---|
| High risk threshold | 5 or more weighting points | 4 or more weighting points |
| Higher-risk ship types (2 points) | Chemical tanker, gas carrier, oil tanker, bulk carrier, passenger ship, NLS tanker | The same list plus container ships |
| Black-listed flag | 2 points (higher risk bands) or 1 point (medium risk band) | 1 point, no banding |
| Detentions parameter | 2 or more in previous 36 months: 1 point | 3 or more in previous 36 months: 1 point |
| Deficiency history | Cannot add points toward high risk | Inspections recording more than 5 deficiencies count toward high risk |
| Company with no inspection in 36 months | Not scored as such | 2 points |
| High risk window | 5 to 6 months | 2 to 4 months |
| Standard risk window | 10 to 12 months | 5 to 8 months |
| Low risk window | 24 to 36 months | 9 to 18 months |
| Where to check | THETIS and the Paris MoU ship risk calculator | Tokyo MoU PSC database (APCIS) |
Two rows deserve a second look. A container ship, invisible as a type in the Paris scoring, starts with 2 points in the Tokyo region and reaches high risk with little else on the record. And because Tokyo counts heavy-deficiency inspections toward high risk while Paris does not, a ship that repeatedly logs six or seven deficiencies without ever being detained can drift into the high risk class in Asia-Pacific while staying standard risk in Europe. The full Paris mechanics, weighting table included, are in the Paris MoU Ship Risk Profile explained.
Why can a flag be white-listed in one and grey-listed in the other?
Because each MoU builds its own list from its own inspections. Both publish white, grey and black flag lists annually, calculated from the inspection and detention history of each flag's ships over the preceding three calendar years, and the data sets barely overlap. The ships a flag sends to Asia-Pacific ports are often a different slice of its fleet than the ones trading Europe, inspected by different officers with different regional priorities.
So the same registry can be white in Rotterdam and grey in Singapore, and the consequences follow the region: the flag's ships get extra weighting points, and under the Paris MoU a grey or black listing also changes the ship's exposure to banning. A flag with too few port calls in a region may not appear on that region's list at all, which leaves its ships scored without the flag parameter rather than favourably.
Check both lists each July. They are refreshed annually from each MoU's annual report, and a reclassification moves every ship on that flag overnight.
Does the Tokyo MoU ban repeat offenders like the Paris MoU does?
No. The refusal-of-access order is a Paris MoU instrument. Under Section 4 of the Paris Memorandum, a ship on a grey-listed flag detained more than twice in 24 months, or on a black-listed flag detained more than twice in 36 months, is refused access to every port and anchorage in the region. The first ban runs a minimum of 3 months, the second 12, the third 24, and a further detention after the third ban makes the refusal permanent. What that escalation costs an operator commercially is covered in detention costs and consequences.
The Tokyo MoU took a different route. A ship detained three or more times in the last 12 months goes onto its published under-performing ships list, and every member authority is alerted to inspect it at each port call. The ship keeps its trading rights but loses any predictability: in effect, permanent Priority I. Neither mechanism forgives quickly, and both are driven by the same input, detentions, which is why a structured pre-inspection routine pays off identically in both regions even though the penalty curves differ.
Which regimes matter for a fleet trading across regions?
Any regime whose ports the ship actually calls at, and they do not share records. A vessel trading Europe to Asia holds a Paris profile and a Tokyo profile, each built only from inspections inside that region. A clean two years in the Paris MoU leaves the Tokyo profile untouched, and a ship that has been out of a region for long enough loses its low-risk eligibility there simply for lack of an inspection. Add the US Coast Guard, which runs its own targeting matrix outside both MoUs, and the smaller regional MoUs (Indian Ocean, Black Sea, Mediterranean and others) that follow similar models with their own data.
What keeps a cross-trading fleet ahead of this is unglamorous. Track each ship's profile per region, not one global figure. Time pre-inspection walk-throughs to the tightest applicable window, which for Asia-Pacific trade usually means the Tokyo one. And treat the joint campaigns as the moment the regimes converge: the two MoUs increasingly run their Concentrated Inspection Campaigns together, as with the 2026 cargo securing CIC, so the same themed questionnaire meets the ship in Hamburg and in Busan. Where PSC sits against class, flag and commercial vetting is mapped in vetting vs class vs flag vs PSC.