On January 28, 2021, a Special Chamber of the International Tribunal for the Law of the Sea (ITLOS) delivered a judgment in which it rejected preliminary objections raised by the Maldives in arbitral proceedings instituted by Mauritius, concerning the delimitation of the maritime boundary north of the Chagos Archipelago in the Indian Ocean.

On February 5, 2021, the Pre-Trial Chamber (PTC) of the International Criminal Court (ICC) delivered its decision on territorial jurisdiction in the “Situation in Palestine.” The result reflects the controversy surrounding the process and the merits: a divided bench, with a Minority decision three times the length of that of the Majority. The outcome marked the culmination of sustained attempts by Palestinians and their supporters over more than two decades to engage the ICC, beginning with contentious negotiations preceding the vote on the Rome Statute at the Rome Conference and including three preliminary examinations, the third of which concluded with this decision. The Rome Statute, adopted by vote on July 17, 1998, included elements that negotiators acknowledged had never appeared before in international law, and were directed at an Israeli target. For this reason, in large part Israel, which had long supported the principle of an international criminal court, chose not to become a state party to the Statute or to participate in the proceedings.

On December 18, 2020, the International Court of Justice (ICJ) handed down its decision on the jurisdiction of the Court in the case concerning the Arbitral Award of 3 October 1899 (Guyana v. Venezuela). By a 14–2 majority, the Court ruled that it has jurisdiction to decide certain elements of the application submitted unilaterally by Guyana against Venezuela, while it concluded unanimously that it lacks jurisdiction over other aspects of Guyana's application. Having established jurisdiction over certain elements of Guyana's application, the ICJ will now proceed to hear the merits of the claims.

In 2021, Hong Kong's electoral system underwent its most significant reform since the People's Republic of China (PRC) resumed the exercise of sovereignty over Hong Kong on July 1, 1997. By a decision adopted on March 11, 2021 to “improve the electoral system of the Hong Kong Special Administrative Region and develop a democratic system suited to the actual situation of the Hong Kong Special Administrative Region” (HKSAR), the National People's Congress (NPC) decided to amend the methods of selecting the Chief Executive of the HKSAR and forming the Legislative Council of the HKSAR (LegCo). The existing Election Committee would be reformed and given a pivotal role in the elections of the Chief Executive and LegCo members. A new candidate qualification review committee would be established to qualify all candidates. The Standing Committee of the National People's Congress (NPCSC) was empowered to amend the first two annexes of the Basic Law of the Hong Kong Special Administrative Region of the People's Republic of China (Basic Law), which specify the methods for selecting the Chief Executive and forming the LegCo. The HKSAR would amend local election laws to implement the reforms and organize future elections in accordance with the law. The Chief Executive would submit timely reports to the Central People's Government. The NPC Decision was adopted with 2,895 votes in favor and one abstention.

The appellants originally brought this case against the World Bank Group's financing arm, the International Finance Corporation (IFC), alleging that IFC negligently funded (via a company based in India) a power project in India that damaged the appellants' environment, health, and livelihoods. The issue of whether IFC was immune from suit under the International Organizations Immunities Act of 1945 went to the Supreme Court, which decided in 2019 that international organizations enjoy the same immunity from suit that foreign governments enjoy under the Foreign Sovereign Immunities Act—meaning that they can be sued in the U.S. if their actions fall within one of the exceptions to the FSIA, including the exception for “commercial activities.” The Supreme Court's decision was published in full in Volume 58, Issue 3 of International Legal Materials. This was a reversal from existing jurisprudence, which had held that international organizations (unlike foreign governments) had near-absolute immunity from lawsuits under the Foreign Sovereign Immunities Act and the International Organizations Immunities Act. The case was remanded to the D.C. District Court, which dismissed the complaint in February 2020 because the “gravamen” of the complaint occurred outside the U.S., rendering the commercial activities exception inapplicable. Budha Jam et al. appealed that decision to the D.C. Circuit Court, which affirmed the lower court's decision in July 2021. The Court rejected the appellants' argument that the significant activity was IFC decision-making in the U.S., agreeing with the District Court that the gravamen of the complaint occurred outside the U.S.