Under customary international law, a nation state’s courts have jurisdiction over crimes where there is some link, usually territorial, between that state and the crime. In addition, under customary international law and certain treaties, a state has universal jurisdiction over certain crimes of international concern regardless of where the crime was committed or the nationality of the victim or perpetrator. These crimes of international concern are (a) piracy; (b) slavery; (c) war crimes; (d) crimes against peace; (e) crimes against humanity; (f) genocide; and (g) torture.
Amnesty International recently released a comprehensive review of domestic statutes regarding criminal jurisdiction in the 193 members of the United Nations. It found that 75% of the members provided for universal jurisdiction over one or more of the above crimes. Yet there are many obstacles to effective use of these jurisdictional statutes. States often incorporate incomplete or incorrect definitions of such crimes into their domestic codes. Another obstacle is incorporation of defenses that are inconsistent with the international law for these crimes: following superior orders; statutes of limitation; amnesty laws; pardons; and immunities.
On the other hand, this study found only 19 states have actually invoked universal jurisdiction since World War II. They are Argentina, Austria, Australia, Belgium, Canada, Denmark, Finland, France, Germany, Israel, Netherlands, Norway, Paraguay, Senegal, Spain, Sweden, Switzerland, the United Kingdom and the U.S.
As we have seen, one of these 19 states–Spain–currently is invoking its domestic statute that implements the principle of universal jurisdiction for its criminal prosecution of former Salvadoran military officers for the November 1989 murders of the six Jesuit priests and their cook and her daughter at the Universidad de Centro America in San Salvador. Spain’s statute provides that its National Court (La Audiencia Nacional) has universal jurisdiction for war crimes, genocide, crimes against humanity and torture.
In 2009 Spain adopted an amendment that added the following conditions or limitations on such jurisdiction: (1) the alleged perpetrators are in Spain; or (2) the victims are of Spanish nationality; or (3) there is another connecting link to Spain. In addition, the amendment specified that for such Spanish jurisdiction to exist another country or international tribunal had not started a process involving an investigation and successful prosecution of such offenses; if there is such another process, then the Spanish court should suspend or stay its case until the other investigation and prosecution has been concluded. The latter provision is referred to as the subsidiary principle.
This amendment has been seen by some as a significant and regrettable limitation on universal jurisdiction in Spain. In my opinion, however, the amendment is a reaffirmation of Spain’s implementation of such jurisdiction, and the limitations are reasonable to make efficient use of Spanish judicial resources. Moreover, the subsidiary principle is similar to the International Criminal Court’s notion of complementarity whereby the ICC does not take a criminal case if there is a good faith criminal investigation or prosecution in a national court system or a good faith decision by a state not to prosecute. The same considerations find expression in the U.S. notions of comity or forum non conveniens whereby a civil case in an U.S. court is stayed or dismissed if it makes more sense for the case to be litigated in another country.
 David Weissbrodt, Fionnuala Ní Aoláin, Joan Fitzpatrick, and Frank Newman, International Human Rights: Law, Policy and Process, at 572-86 (4th ed. 2009); Princeton Project on Universal Jurisdiction, Princeton Principles on Universal Jurisdiction (2001). Especially noteworthy is a blog exclusively devoted to universal jurisdiction: http://ergaomnesnet.wordpress.net.
 Amnesty Int’l, Universal Jurisdiction: A Preliminary Survey of Legislation Around the World (Oct. 2001 [“AI Study”]; van Schaack, Amnesty International Universal Jurisdiction Study, IntLawGrlls (Nov. 30, 2011).
 Post: International Criminal Justice: Spanish Court’s Case Regarding the Salvadoran Murders of the Jesuit Priests (Aug. 26, 2011); Post: International Criminal Justice: Spanish Court Issues Criminal Arrest Warrants for Salvadoran Murders of Jesuit Priests (May 31, 2011); Post: International Criminal Justice: Developments in Spanish Court’s Case Regarding the Salvadoran Murders of the Jesuit Priests (Aug. 26, 2001); Post: Spain Requests Extradition of Suspects in Jesuits Case (Dec. 3, 2011).
 AI Study at 105; Human Rights Watch, Universal Jurisdiction in Europe, ch. XII (June 27, 2006). The Criminal Division of the Spanish National Court in Madrid has six chambers. An instructing (or investigative) judge presides over each chamber. Once an instructing judge accepts a criminal case, that judge initiates an investigation. After the completion of the investigation, the instructing judge closes the case and transfers it within the court to a panel usually of three judges who will preside over the trial or “oral phase” of the case. Such criminal cases are commenced by ordinary citizens filing a criminal complaint. If a victim files the complaint directly with an instructing judge, then the victim becomes a party to the case for further proceedings. This is known as a private prosecution (acusacion particular). (Center for Justice & Accountability, The Spanish National Court: An Overview of La Audiencia Nacional, http://www.cja.org/article.php?id=342&printsafe=1.)
 Spain, Government Gazette No. 266, Law I/2009, First Article (Nov. 4, 2009) (amendment to Article 23.4 of Organic Law 6/1985) (Google English translation); Burnett & Simons, Push in Spain to Limit Reach of the Court, N.Y. Times (May 20, 2009); Burnett, Spain Votes on Changes to Inquiry Law, N.Y. Times, (June 26, 2009); Assoc. Press, Spain Shortens Long Arm of Justice, N.Y. Times (Oct. 15, 2009).
 Center for Justice & Accountability, Bill Restricting Spain’s Universal Jurisdiction Law Passes First Round of Voting, http://cja.org/article.php?id=666 (circa June 25, 2009); Human Rights Watch, The world needs Spain’s universal jurisdiction law (June 27, 2009).
 Post: International Criminal Court: Introduction (April 28, 2011).