Post-Soviet Maritime Boundary Delimitation in the Baltic Sea

December 5, 2023
IMA Research Team

By Alex Marsh

The Baltic Sea, despite being comparatively well-delimited relative to other bodies of water, remains an interesting case study in the novel application of maritime boundary law, as well the effect of historical and geopolitical tensions on boundary negotiation. Many of the complexities related to maritime boundary delimitation in the Baltic Sea can be traced to a 1988 Agreement between the Kingdom of Sweden and the Union of Soviet Socialist Republics (USSR), and the subsequent collapse of the USSR a few years later.

Sweden’s 1988 Agreement with the USSR established a multi-purpose boundary between the two party’s continental shelves and fishery zones. Crucially, this agreement did not apportion separate boundaries for each soviet satellite state in the Baltic region (Latvia, Lithuania, and Estonia, referred to hereafter as “the Baltic states”). Rather, the agreement created one boundary for the entirety of the USSR’s Baltic coast.

After the fall of the USSR in 1991, having regained their independence, the Baltic states argued that the maritime boundaries created for them by the USSR were not valid on the basis that the modern-day states of Latvia, Lithuania, and Estonia were not successors to the USSR member states of the same names, but to the preceding independent, pre-World War II republics. The Baltic states maintain they were illegally annexed by and incorporated into the USSR following World War II, and as such, international law should not treat boundaries negotiated by what was, in their view, an occupying power, as legitimate in light of their newfound independence.

Sweden (and to a lesser extent, Finland), maintained that the boundary negotiated with the USSR was valid and legitimate, a position strongly supported by the newly christened Russian Federation. Of note, the Russian Federation included language in their 2005 tripoint agreement with Lithuania and Sweden explicitly referring to the existence of the 1988 Agreement in support of this position. Sweden had no desire to renegotiate the existing boundary, which had resulted in a favorable resolution for Sweden, since it had taken a significant amount of time to agree upon the confines of the 1988 boundary due to disputes concerning fishery rights and the status of outlying islands between both parties.

Further complicating matters, the independence of the Baltic states necessitated the negotiation of bilateral maritime boundaries between those states, as well as tripoints where those new boundaries would inevitably intersect with existing boundaries, including the disputed Sweden–USSR boundary. With the Baltic states firmly against recognizing the Sweden–USSR boundary, and Sweden maintaining the boundary’s legitimacy, a workaround emerged that introduced a largely novel concept into the corpus (body) of international maritime law.

Typically, agreements creating or amending maritime boundaries are negotiated between the contracting parties by listing, at minimum, a set of coordinate points that make up the boundary, the method of connecting these points (i.e., a straight line, the arc of a great circle, etc..), and the datum used to list the coordinate points.

The Baltic states eschewed this procedure when negotiating tripoints with Sweden (specifically, the Sweden-Latvia-Lithuania and Sweden-Latvia-Estonia tripoints). Latvia negotiated bilateral agreements with Lithuania and Estonia, respectively, whose final points were not a defined coordinate. Instead, the agreement specified an azimuth along which the bilateral boundary would extend until encountering the maritime boundary of a “third state” (Sweden). By doing this, the Baltic states de facto recognized the existence of Sweden’s previously-defined maritime boundary without addressing the validity of the Sweden–USSR agreement, despite that agreement creating the same maritime boundary upon which the Latvia-Lithuania and Latvia-Estonia boundaries abut. The bilateral agreements and subsequent tripoint agreements between the Baltic states and Sweden do not make mention of the 1988 Sweden–USSR boundaries, with the Sweden-Latvia-Estonia tripoint agreement only listing a singular coordinate point to clarify the exact location of the tripoint. The Sweden-Lithuania-Russia tripoint, however, does note that the tripoint sits upon the historical 1988 Sweden–USSR boundary.

In another novel application of maritime boundary law, the entire maritime border between Sweden and Latvia does not appear to be explicitly acknowledged. Latvia’s bilateral agreements with Estonia and Lithuania use the aforementioned technique of specifying an azimuth which runs until encountering Sweden’s claimed maritime border. These two tripoints effectively serve as the de facto endpoints of the Sweden-Latvia maritime border, as no official agreement has been concluded between the two states, in part to avoid legitimizing the border drawn by the USSR. Even though Latvia is evidently content with the existing border on geographic and economic grounds, it is politically unfeasible for them to recognize a boundary drawn by the USSR, leading to the existing status quo. A bilateral agreement may eventually be concluded, but as of yet no efforts appear to have been made in this regard.

Ultimately, little changed in terms of the geographic location of the fateful 1988 Sweden–USSR boundary. Sweden prevailed in protecting the concessions it had gained during negotiations with the USSR, and maintained the boundary in its existing location. However, the Baltic states also largely prevailed in avoiding legitimizing the 1988 boundary. Bilateral and tripoint agreements exclusively between the Baltic states and Sweden used novel methods of delimitation to avoid acknowledgement of the 1988 border while still accomplishing (at least de facto) the delimitation of the new national boundaries in the area.

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