The respective decree of the Ministry of Infrastructure is expected to be promulgated and enter into force in the nearest days. It's too early to make predictions in respect of the consequences of vessel calls into Crimean ports, however the experts are unanimous that the closure of the ports may give Ukraine and other countries the formal reasons to inspect or even detain under the requirements of ISPS Code the vessels visited Crimea.

There is an opinion that a port facility is only considered ISPS compliant when it is listed in the IMO’s security database as such. The IMO accepts confirmation of a port’s ISPS compliance only from the respective national government. As the UN agency, the IMO is unlikely to accept a statement of ISPS compliance from the Russian authorities for any Crimean port, despite Russian Federation already included Crimean ports in its ports list.

Therefore, when a renewal of this confirmation is required, or should the Ukrainian authorities decide to inform the IMO that it has revoked its acceptance of certain or all international Crimean ports’ ISPS compliance, then the applicable ports will no longer be ISPS compliant, and in theory would not be suitable ports of call for any ISPS compliant vessel.

According to IMO "Guidance relating to the implementation of SOLAS Chapter XI-2 and the ISPS Code" (MSC/Circ.1111) and Resolution MSC.159(78) "Interim Guidance on control and compliance measures to enhance maritime security", The Contracting Government may, in ensuring compliance with SOLAS Chapter XI-2, require that ships intending to enter its ports provide specific security-related information.

If the assessment of the available information relating to the ship establishes clear grounds for believing that the ship is in non-compliance with the requirements of chapter XI-2 or part A of the ISPS Code, the Contracting Government shall attempt to establish communication with and between the ship and the Administration and/or the recognized security organization in order to rectify the non-compliance.

Examples of possible clear grounds which may be determined prior to a ship entering port include the evidence or reliable information that the ship has embarked persons, or loaded stores or goods at a port facility which is in violation of chapter XI-2 or part A of the ISPS Code, and the ship in question has not completed a Declaration of Security, nor taken appropriate, special or additional security measures or has not maintained appropriate ship security procedures.

When such clear grounds exist, a Contracting Government may take following actions:
(a) Allow ship into port, and to impose one or more control measures, including inspection of the ship, delaying the ship, detention of the ship, restrictions of operations including movement within the port, and/or additional or alternative lesser administrative or corrective measures;
(b) Require that the ship proceed to a specified  location in the territorial sea or internal waters of the Contracting Government in order to enable the inspection of the ship;
Source: Interlegal