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HomePassing through? Russian Vessels in the Danish Straits

Passing through? Russian Vessels in the Danish Straits

2 April 2024

The EU has as a consequence of Russia’s illegal invasion of Ukraine adopted a wide regime of sanctions which significantly affects maritime trades of Russian goods. The Danish Straits qualify as European waters meaning that the Russian sanctions will apply to vessels in these waters. Special considerations come into play for the Danish Straits, however, as international law dictates that Denmark cannot prohibit transit passage of foreign vessels unless the vessels appear to be violating the international rules on marine pollution prevention. In this newsletter, we will describe the main divergences of EU and international law and how this may affect the enforcement of the sanctions in practice.


EU’s Russian Sanctions

The European Union has by March 2024 adopted no less than thirteen sanction packages against the Russian Federation following the invasion of Ukraine. The sanctions are partly contained in Regulation 833/2014 of 31 July 2014 (as amended) (the “Regulation”)[1]. For an update on the most recent sanctions and the specific impacts on tankers, we refer to our recent newsletter accessible here and here.

The Regulation prohibits the import and transfer of a long list of goods originating in Russia, including certain types of coal, charcoal, fuel wood and petroleum products (above the price cap), through European territorial waters (the “Prohibited Trades”)[2], among a long list of other restrictions. The Regulation applies irrespective of the final destination of the products being outside of the EU. The mere transit through EU territory is thus sufficient for the Regulation to apply to the Prohibited Trades.

The Regulation applies to the territory of the EU, to any EU national, to any vessel registered in an EU member state and to any legal person domiciled or doing business in the EU[3].


The status of the Danish Straits

The Danish Straits (the Sound, the Great Belt and the Little Belt) constitute the main gateway between the Baltic Sea and the Atlantic Ocean and are among the world’s major traffic routes. The Straits still play a key part in the export of Russian goods.

Historically the Straits were subject to the almost absolute control of the Danish king. Commencing in the early 15th century, the Kingdom of Denmark demanded the payment of toll for any vessel passing the Sound (the “Sound Toll”) with the threat of requisition for any vessels not declaring the fair value of the goods. This was generally possible to enforce due to the short distance between Elsinore (Hamlet’s city), Denmark, and Helsingborg (historically a Danish possession, today a part of Sweden) of only about 4 km.

In early customary international law, the Danish enforcement of control over the straits was generally accepted under the “cannon-shot” rule, permitting states to exercise control over coastal waters based on the reach of the coastal states’ cannons.

Nonetheless, following increasing international pressure, Denmark agreed in the 1857 Copenhagen Treaty[4] to abolish the Sound Toll and to allow, in perpetuity, the free, unrestricted passage of foreign, commercial vessels through the Straits against a one-time payment of large lumpsums by each of the contracting states to the convention, states which included the UK, France, Prussia and the Russian Empire. The Danish Straits were thus among the first international straits with a treaty-based free right of transit.


Transit passage under international law

The framework for the jurisdiction of the coastal states and rights of other states have been set out in the United Nations Convention on the Law of the Sea in 1982 (“UNCLOS”).

UNCLOS, Part III, allows for the innocent passage/transit passage of foreign vessels through straits used for international navigation[5]. The exercise of coastal jurisdiction is limited in respect of (i) the power to regulate the straits (e.g. the banning of transport of certain goods), (ii) the power to enforce such laws and (iii) the power to sanction violations of such laws (i.e. prescriptive, enforcement and criminal jurisdiction). Depending on the type of activity, these factors will limit the jurisdiction of the coastal state.

The general rule set out in UNCLOS is that all foreign vessels, including warships, have the right of uninterrupted transit passage if the vessel “proceeds without delay” and does not use threat or use of force against the coastal states or otherwise infringe on the peace and security of the coastal states under the UN Charter[6]. The coastal states’ prescriptive jurisdiction is limited under UNCLOS to non-discriminate laws to ensure safe navigation, protect the environment and the loading/unloading of goods and issues relating to customs, fiscal, immigration or sanitary matters[7].


The regime applicable to the Danish Straits

Importantly, UNCLOS explicitly provides that the general rules on the right of transit passage do not apply to straits for which long-standing treaties apply, see UNCLOS, Art. 35 (c). It is the position of the Danish government that the 1857 Copenhagen Treaty constitutes such a convention under Art. 35 (c) meaning that UNCLOS, Part III, Section 2, does not apply to the Danish Straits[8]. It is generally accepted that the 1857 Copenhagen Treaty is supplemented by customary international law as generally codified in the UNCLOS. In any event, no significant differences appear to exist between the 1857 Copenhagen Treaty and the UNCLOS. The 1857 Copenhagen Treaty, Art. 1, also explicitly prohibits Denmark from suspending the free transit of merchant vessels.


The Application of the Regulation to the Danish Straits

The Straits mainly lie within Danish territorial waters, the Sound partly in Swedish waters or, put differently, fully within the territory of the European Union. The Regulation thereby applies to Prohibited Trades via the Danish Straits. The EU has acceded UNCLOS, which has thereby become part of the compound EU legal order. Any conflict of law between the Regulation and UNCLOS is thus not immediately solved by the primacy of EU law (which would otherwise supersede Danish domestic law).

This gives rise to an obvious conflict with the right of international transit through the Danish Straits, as the mere carriage of goods, such as coal, charcoal, steel, wood and petroleum products covered by the Prohibited Trades is in principle covered by the right of transit passage under the 1857 Copenhagen Treaty (and UNCLOS, Part III, Section 2).

The Danish authorities will thus, as a matter of international law, largely be hindered from enforcing the transit prohibitions contained in the Regulation on foreign vessels. The Danish authorities would potentially be permitted to take actions if consent is obtained from the vessel’s flag authorities. Arguably, such consent can in some scenarios possibly be implied from the Regulation in respect of EU-flagged vessels[9].

For completeness, we note that if the vessel performs other activities while in Danish waters, e.g. ship-to-ship transfers, the vessel would no longer be in transit passage (or innocent passage). The Danish authorities may potentially enforce the Regulation in respect of the ship-to-ship operation itself. Based on the principle of proportionality[10], the Danish authorities would likely not be empowered under UNCLOS to limit the vessel’s ability to actually enjoy its right under the 1857 Copenhagen Treaty and thus to allow the vessel to, subsequently, complete its free transit through the Danish Straits.


Application of UNCLOS on other grounds

First, shipowners (or other vessel interests) may not necessarily be protected in the event of an enforcement action by the international law defence as a matter of domestic law. The Danish legal system is based on dualism, meaning that domestic law and international law are separated. As a starting point, private entities cannot rely on international law to support the assertion that ‘domestic laws’ (such as the Regulation) are invalid; any violation of international law is a matter for the vessel’s flag state, not the owners.

This starting point is, however, not absolute. The fact that EU has acceded UNCLOS means that each provision in UNCLOS can have direct effect (i.e. be invoked by private entities) if the provisions meet the relevant EU law criteria for direct effect.[11] To the best of our knowledge, the EU Courts have not ruled on the direct effect of the UNCLOS right of free transit, and it is thus unclear to what extent private individuals may rely upon it.

Even if shipowners may invoke defences against any enforcement action while the vessels are in transit, this will not protect the parties against indirect sanctions such as the seizure of assets in Danmark or other jurisdictions enforcing the Regulation.

Importantly, the restrictions which apply to Denmark’s powers as coastal state will not apply to the flag state. The vessel is subject to the jurisdiction of the flag state under the flag state principle also enshrined in UNCLOS[12]. If the flag state is an EU member state, the vessel is thus subject to the Regulation based on that flag. The flag state may thus potentially enforce the Russian sanctions when Denmark cannot. In practice, however, the vessels of the Russian dark fleet will surely not use EU flags.

While UNCLOS restricts the powers of non-flag states to prohibit the transport of certain goods (under the Russian Sanctions) in the Danish Straits, international law does generally not restrict the powers of a state to sanction the international trading activities of a company domiciled in that state (at least provided the sanctions are compatible with the framework underlying the WTO[13]). If EU-domiciled ship owners facilitate the trading of prohibited cargoes, authorities in the EU will likely seek to enforce the sanctions on such grounds against any owners who are domiciled or doing business in the EU.


Risk of environmental damage

The focus has for a long time been on the enforcement of the Russian Sanctions (or lack thereof). More recently, light has been cast on the safety risks relating to the conditions of the often older tankers transporting Russian oil or serving Russian interests.

Lloyd’s List has thus reported that significant numbers of vessels carrying Russian oil through Danish waters have dubious safety records or do not possess adequate insurance cover[14]. Many tankers have also continuously rejected use of Danish pilots. In early March 2024, a collision in Danish waters involving a tanker again led to press reports highlighting the difficulty of asserting the ownership and insurance cover on the vessels. In the particular case, the owners had, however (unlike many other tanker operators) actually engaged a pilot from the DanPilot. Furthermore, the Danish Maritime Authority inspected the vessel and could confirm that the tanker had all the required insurance certificates in place. The vessel was therefore cleared to proceed to undergo repair works.

The incident has nonetheless created awareness of the risk of tankers without the insurance cover required under the 1992 Civil Liability Convention covering liability for tanker oil pollution damage[15]. In essence, without insurance cover, the Danish authorities would likely need to cover the clean-up costs in the event of a major oil spill. It is therefore crucial for Denmark as a coastal state to have the power to inspect the vessels.

Importantly, UNCLOS, Art. 220 (2) allows for an exception to the principle of free, transit passage if there are “clear grounds for believing that a vessel has […] during its passage therein, violated […] applicable international rules and standards for the prevention, reduction and control of pollution from vessels.” In such case, Denmark may thus as coastal state physically inspect and detain the vessel if it is found not to have the required certificates and insurances in place in respect of the 1992 Civil Liability Convention. The provision even allows, if the vessel’s violation (e.g. lack of insurance or safety risks) constitute a major threat of major damage to the coastline or other interests of Denmark, to institute proceedings against the vessel and detain the vessel as required.

Denmark will still be subject to the principle of proportionality and may therefore likely not enforce Russian Sanctions even following a lawful detention of such vessels (based on the environmental concerns). The right of free transit passage may not be impaired for longer as the lawful enforcement of environmental protection rules may require.


Closing remarks

EU’s sanctions against Russia are difficult to enforce in the Danish Straits under international law. The Regulation may, however, indirectly apply to many parties and the authorities in the EU Member States, including Denmark, are obliged to seek to enforce the sanctions. The lack of enforcement against vessels in transit passage should thus not limit the authorities’ resolve in tracking unlawful activities in Danish waters.

Still, the enforcement of the environment-focused rules against tankers and the requirement for insurances may – combined with growing isolation of Russian interests – be a more efficient manner for the Danish authorities to indirectly impact the Russian activities. Such actions may at least reduce risks relating to major oil spills and sea safety incidents involving the ‘dark fleet’ which are circumventing the sanctions.

Initial statements by the Danish minister of environmental affairs indicate a willingness to enhance the supervision and control of tankers. We are though yet to see if the Danish authorities will be successful and whether other member states will follow suit.

Gorrissen Federspiel advises ship owners, charterers, managers and other businesses with ensuring compliance with the EU, UK, US and international sanctions against Russia in the maritime and other business sectors. However, Gorrissen Federspiel does not, as a matter of company policy, assist any Russian companies or individuals.



[1] Regulation 833/2014 concerns a wide range of restrictions. Other EU sanctions concerning Russia include Regulation 269/2014 (as amended) concerning asset freezes, Regulation 692/2014 (as amended) concerning activities in Crimea/Sevastopol.

[2] The Regulation, Art. 3g, 3i, 3m, 3n, 3o and 3p, see Annexes XVII, XXI, XXV, XXVI and XXXVIIIA.

[3] Regulation, Art. 13.

[4] The Treaty between Great Britain, Belgium, France, Hannover, Mecklenburg-Schwerin, Oldenburg, Netherlands, Prussia, Russia, Sweden and Norway, and the Hanse Towns, on the one part, and Denmark, on the other part, for the Redemption of the Sound Dues, signed at Copenhagen, 14 March 1857.

[5] See UNCLOS, Art. 44.

[6] See UNCLOS Art. 38 and 39 (1).

[7] See UNCLOS, Art. 39 (2)).

[8] See the declaration by the Kingdom of Denmark relating to Art. 35 (c) of the UNCLOS, see the Law of the Sea Information Circular (LOSIC No. 21, April 2005), p. 2. See also the Kingdom of Denmark’s submissions in connection with the ICJ Great Belt Bridge- case (Finland v Denmark), Counter Memorandum, 18 May 1992.

[9] The Commission has in its consolidated FAQs on the implementation of the Regulation as of 25 March 2024 (p. 31, question 28) noted that the Member States can take actions to enforce the Regulation also in the territorial sea. The Commission includes the explicit reservation, however, that the member state may take into regard the vessel’s “freedom of navigation”, i.e. the right of innocent (transit) passage.

[10] See e.g. the Permanent Court of Arbitration’s award in the Duzgit Integrity-case (Malta v São Tomé and Príncipe) (Case no. 2014-07), 5 September 2016, concerning excessive actions on a STS transfer.

[11] See for instance case 87/75, Bresciani v. Amministrazione, para. 16, in which the EU Court confirmed that provisions in international treaties acceded by the EU may have direct effect where two criteria are met: (i) the spirit, structure, and nature of the agreement, and (ii) the wording of the provision are both intended to create individual rights.

[12] UNCLOS, Art. 92.

[13] See for instance Art. XXI under the GATT 1994 (the ‘security exception’).

[14] Article on Lloyd’s List: Talks underway for Denmark ‘to stop and inspect’ sanctions-breaching tankers from Russia :: Lloyd’s List (

[15] International Convention on Civil Liability for Oil Pollution Damage, 1992. The convention is incorporated in the Danish Merchant Shipping Act, Ch. 10.

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