[1] The first and foremost restriction imposed by international law on a State is that—failing the existence of a permissive rule to the contrary—it may not exercise its power in any form in the territory of another State.The policing of transnational and international crimes is a challenge to state-based law enforcement agencies, as jurisdiction restricts the direct intervention a state's agencies can legally take in another state's jurisdiction, with even basic law enforcement activities such as arrest and detention "tantamount to abduction" when carried out extraterritorially.
[3] These explicit limits on extraterritorial law enforcement operations has therefore instead encouraged co-operation between law enforcement agencies of sovereign states, forming supranational agencies such as Interpol to encourage co-operation, and placing additional obligations on the state such as aut dedere aut judicare ("extradite or prosecute") to compel prosecution of certain types of transnational crime, including hijacking of civilian aircraft, taking of civilian hostages, and other acts of terrorism, as well as crimes against diplomats and other "internationally protected persons".
As Stigall points out, innate in 'just' war (jus ad bellum) is the expectation that one state may be conducting military activity against, and within the borders, of another state; the laws of armed conflict "[presuppose] extraterritoriality".
[7] For the Council of Europe, key tenets of its human rights law jurisdiction are laid down in Article 1 of the European Convention on Human Rights (ECHR), with the convention employed to complement and reinforce the more specific scope of humanitarian law.
[8][a] The application of this to extraterritorial operations has been noted by Ryngaert as mixed, with Al-Skeini and others v United Kingdom in 2011 attempting "to square Bankovic [v. Belgium's 'sufficient control' model of jurisdiction] with the personal model of jurisdiction",[9][10] and Al-Jedda v United Kingdom "tried to reconcile the 'ultimate control and authority' standard ... with the 'effective operational control' standard endorsed by the UN's International Law Commission.