Jus cogens is a Latin term meaning “compelling law” and refers to certain international norms that are considered of such high authority that they have peremptory effect on other norms and legal obligations.  For this reason, jus cogens norms are also referred to interchangeably as peremptory norms.  While the modern use of the term jus cogens to refer to peremptory norms evolved in the 20^th century after the atrocities of World War II, early international legal scholars such as Hugo Grotius and Emmerich de Vattel differentiated between ordinary legal obligations derived from treaty or custom and the “internal” or “necessary” law of nations derived from natural law and moral principles.

Article 53 of the Vienna Convention on the Law of Treaties defines a peremptory norm as “a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.”  Because peremptory norms are of supreme authority, states may not derogate from them through a treaty.  As provided in Article 53, “[a] treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law.”  The validity of treaty obligations that violate a peremptory norm are also addressed in the Restatement (Third) of Foreign Relations Law of the United States.  As indicated in § 331(2), an international agreement is void if it violates a peremptory norm. 

The specific acts that constitute a violation of a jus cogens norm are not enumerated in the Vienna Convention on the Law of Treaties.  In the United States, however, some guidance is provided in the comments and reporters’ notes to the Restatement (Third) of Foreign Relations Law of the United States.  Although § 102 of the Restatement defines customary international law generally, Paragraph 6 of the Reporters’ Notes to § 102 further explains that although the specific norms that constitute jus cogens are not universally agreed upon, they do include the United Nations Charter principles prohibiting the use of force and norms that create “international crimes.”  According to the Reporters’ Notes, such “international crimes” might include rules prohibiting genocide, slave trade and slavery, apartheid and other gross violations of human rights.

In the United States, violations of peremptory norms are generally enforced through the Alien Tort Statute, 28 U.S.C. § 1350 (an overview of the Alien Tort Statute is provided in the Winter 2010 issue of the International Judicial Monitor).  The Alien Tort Statute (ATS) establishes jurisdiction in the federal courts over “any civil action by an alien for a tort only, committed in violation of the law of nations or a treaty of the United States.”  Thus far, the only Supreme Court decision interpreting the scope of the ATS is Sosa v. Alvarez-Machain, 542 U.S. 692, 124 S. Ct. 2739 (2004), which suggested that to be actionable, the international norm in question must be specific, universal, and obligatory. 

While Sosa did not address the specific issue of jus cogens norms, the nature and scope of peremptory norms cognizable under the ATS continues to be disputed, even among members of a single court.  For example, the Ninth Circuit in Sarei v. Rio Tinto, PLC, __ F.3d __, 2011 WL 5041927 (9^th Cir. October 25, 2011) recently analyzed the concept of jus cogens to determine the viability of claims brought under the ATS by current and former residents of Papua New Guinea against an international mining group.  The plaintiffs claimed that they had suffered a number of grave human rights violations arising from Rio Tinto’s copper mining operations.  Although the court found that the jus cogens norms prohibiting genocide, war crimes and torture were sufficiently specific to give rise to an ATS claim, it rejected the claim that systematic racial discrimination had risen to this level.  The dissent argued, however, which necessarily gives rise to federal jurisdiction under the ATS.

Beyond the difficulties in determining the scope of jus cogens norms, enforcement often conflicts with international and common law norms relating to sovereign immunity.  Under the Supreme Court’s ruling in Banco Nacional de Cuba v. Sabbatino, 376 U.S. 398 (1964), the Court famously decided that the act of state doctrine precludes the courts of this country from inquiring into the validity of the public acts of a foreign government committed within its own territory.  When the act of state doctrine is used as a shield against claims arising from jus cogens violations, however, many courts have concluded that such actions cannot be considered sovereign public acts for which sovereign immunity should be recognized.  For example, the Ninth Circuit in Siderman de Blake v. Republic of Argentina, 965 F.2d 699, 718 (9th Cir.1992), held that jus cogens norms are exempt from the act of state doctrine simply because no state may derogate from such norms, through treaties or domestic actions. 

The liability of a foreign state for torts arising from jus cogens violations is also subject to the Foreign Sovereign Immunities Act, codified at 28 U.S.C. § 1602 et seq.  For individual government officials, however, the Supreme Court recently held in Samantar v. Yousuf, 130 S. Ct. 2278 (2010) that foreign official immunity is governed by common law, and not the provisions of the Foreign Sovereign Immunities Act.  In addition, heads of state are in certain circumstances entitled to immunity from jurisdiction in foreign courts.  Given this array of foreign governmental immunities, the impact of jus cogens violations on immunity is often disputed and complex. 

The interplay of state immunity and jus cogens is not only litigated in domestic human rights proceedings, but in international tribunals as well.  The most recent and publicized litigation involves claims brought before the International Court of Justice (ICJ) by the Federal Republic of Germany against Italy seeking to prevent the Italian courts from exercising jurisdiction in the continued litigation of human rights violations in Italian courts arising from World War II war crimes violations.  Germany seeks to assert its right to jurisdictional immunity as a sovereign State in these cases following a ruling of the Italian Court of Cassation that while customary law prescribes immunity from the jurisdiction of a foreign state for sovereign acts, such immunity cannot be accorded when such acts amount to jus cogens violations.  In July 2011, the ICJ allowed Greece to intervene in the action, as Germany has also challenged the enforcement in the Italian courts of Greek judgments relating to World War II human rights violations committed by the Nazi party.  Although this case is still pending, the ICJ’s decision may cast considerable light on how American courts will interpret common law immunities in the context of jus cogens litigation in the future.