To what extent, if any, should one country enforce the criminal law of another country?

At first glance, the answer appears to be simple or apparent: one country should not enforce the criminal law of another at all. Criminal law has traditionally been territorial. It is the body of legislation by which a state defines offences, organises the apprehension and trial of suspects, and determines penalties for offenders. This structure has historically been tied to the authority of a particular sovereign state. Criminal law can be defined as the body of law which defines criminal offences and regulates the charging, trial, and consequences of a suspected or convicted person, making clear that criminal law is fundamentally connected to public authority rather than private wrongs (Encyclopaedia Britannica, 2024). State sovereignty, similarly, has long been regarded as resting on a state’s authority to make and enforce rules within a defined political space; as Thomson argues, the ‘bedrock’ of sovereignty lies in rule-making and enforcement authority (Thomson, 1995). Based on this traditional view, it would seem wrong in principle for one state to enforce another’s criminal law, because doing so risks diluting sovereignty, importing foreign legal values into a domestic system, and permitting politically motivated interference under the cover of legal cooperation.

Yet that answer is no longer adequate. Considering our current geopolitical landscape, full of transnational crime, digital communication, and mass movement across borders, a purely territorial model of criminal justice leaves serious gaps in enforcement. Modern transnational crime cannot be contained or confined by borders; rather, criminal groups exploit them. Transnational organised crime can be described as a threat capable of undermining democracy, free markets, and stable societies (Hesterman, 2005). On the other hand, Friedrichs argues that criminology itself has had to move beyond a local or national focus because crime increasingly operates as a transnational and global phenomenon (Friedrichs, 2007). If states insisted on the absolute rule that they would never assist in enforcing another country’s criminal law, offenders could escape justice simply by crossing a border. In that sense, rigid territorialism would not protect liberty; it would create safe havens for terrorists, war criminals, and traffickers. The better answer, therefore, is that one country should enforce the criminal law of another to a significant but limited extent: enough to prevent impunity and uphold justice, but not so far that sovereignty and human rights are sacrificed.

The starting point remains territorial jurisdiction. Territorial jurisdiction is still the primary basis of criminal enforcement because it is the most natural and legitimate ground on which a state acts. Crime usually occurs in a particular place, affects a particular community, and is investigated most effectively where evidence and witnesses are located. The territorial principle therefore reflects not only abstract sovereignty but also practical competence. Even modern discussions of jurisdiction still treat territoriality as the foundational principle from which departures must be justified (The Law to Know, 2024). Thomson’s account of sovereignty reinforces this principle: states have historically claimed exclusive political authority within their territory, and that claim remains central even when cooperation increases (Thomson, 1995). For that reason, one country should not normally prosecute ordinary offences committed wholly within another country merely because it disapproves of the conduct. To allow broad unilateral foreign enforcement would be destabilising, inconsistent with sovereign equality, and open to abuse by powerful states.

However, once crime crosses borders, the case for cooperation becomes far stronger. In our current society, many offences now involve consequences, evidence, and offenders spread across multiple jurisdictions. Drug trafficking may start in one state, travel through a second, and produce negative consequences or harm in a third. Additionally, terrorist financing may be organised online or within one country and channelled through banks in another, ultimately producing violence elsewhere. Cybercrime, trafficking, corruption, and money laundering all expose the limitations of a criminal justice model tied too rigidly to place or territory. Hesterman emphasises that transnational criminal organisations operate similarly to sophisticated multinational corporations. They utilise global networks, specialist knowledge, and rapidly changing technology to maximise profit and evade investigators (Hesterman, 2005). Friedrichs similarly notes that traditional criminal justice institutions were not designed to address crime on this scale (Friedrichs, 2007). In such conditions, some degree of enforcement assistance is not merely desirable but necessary.

The clearest and most established way in which one country enforces another’s criminal law is extradition. Extradition does not mean that the requested state simply becomes an arm of a foreign prosecutor. Rather, it means that one state delivers a person accused or convicted of an offence to the state that claims jurisdiction, so that the latter can try or punish that person. In principle, extradition is a powerful form of cooperation because it prevents fugitives from exploiting borders to escape prosecution. Dugard and Van den Wyngaert note that, as international movement becomes easier and crime takes on a larger international dimension, all nations have an interest in ensuring that suspected offenders who flee abroad are brought to justice rather than allowed to find safe haven (Dugard and Van den Wyngaert, 1998). Gilbert similarly demonstrates that extradition law has evolved through treaties precisely because modern states require reciprocal arrangements for the surrender of fugitives (Gilbert, 1993).

Extradition therefore provides a strong argument that one country should sometimes enforce the criminal law of another. If state A shelters a suspect wanted in state B, state A is, in effect, undermining state B’s criminal justice system. By surrendering that suspect, state A is not renouncing sovereignty but using it cooperatively. The recent closure of the UK Julian Assange extradition case illustrates this point in practice: the Crown Prosecution Service stated that Assange had been granted leave to appeal, then ultimately entered into a plea agreement in the United States, after which the UK proceedings concluded. The case demonstrates both the endurance and the controversy of extradition in modern criminal cooperation (Crown Prosecution Service, 2024). Even where extradition is contested, states evidently accept the broader principle that cross-border surrender is a legitimate tool of enforcing the law.

Nevertheless, extradition also shows why the enforcement of foreign criminal law must be limited. Dugard and Van den Wyngaert argue that extradition law sits at the intersection of two competing imperatives: effective international cooperation in suppressing crime and protection of the fugitive's rights (Dugard and Van den Wyngaert, 1998). Their point is crucial. A state should not extradite automatically merely because another state requests it. Modern extradition law includes safeguards such as double criminality, speciality, and bars on surrender for political offences or where the requested person faces injustice. Gilbert’s discussion of extradition highlights how bilateral arrangements often reflect careful negotiation over issues such as the death penalty and the exact threshold for extraditable offences (Gilbert, 1993). It can be argued that this is the correct model. One country should help enforce another’s criminal law, but only where the offence is genuinely criminal in both systems, the request is lawful, and the receiving state’s procedures satisfy minimum standards of fairness.

Human rights place the strongest outer limit on such cooperation. Dugard and Van den Wyngaert show that human rights law increasingly constrains extradition, especially where the requested individual may be subjected to torture, degrading treatment, discrimination, or an unfair trial in the requesting state (Dugard and Van den Wyngaert, 1998). This is not an accidental complication of extradition; it goes to the heart of the moral legitimacy of enforcement itself. A state cannot justify complicity in abuse by saying it was merely helping another state apply its own law. If extradition or other assistance would expose a person to treatment fundamentally inconsistent with justice, the requested state should refuse. In that sense, the question is not simply whether one country may enforce another’s criminal law, but under what normative conditions it may do so. The answer must include matters such as legality, reciprocity, and respect for basic human rights.

A less dramatic, but equally important, form of foreign enforcement, in comparison to extradition, is mutual legal assistance. Cameron explains that mutual assistance treaties developed to facilitate cooperation in investigating offences, obtaining evidence, and supporting prosecutions, particularly in response to drug trafficking and related cross-border criminality (Cameron, 1989). This mechanism is often preferable to more direct forms of foreign enforcement because it allows each state to remain within its own legal system while still helping another. One state may execute a search warrant or provide banking records, but the act is still carried out under domestic law and judicial control. Mutual assistance therefore offers a balanced answer to the essay question: one country should sometimes help enforce another’s criminal law, not by replacing the institutions of the other state, but by using its own lawful powers to support a prosecution that could not otherwise succeed. This is especially persuasive where the conduct under investigation is itself transnational and the evidence is fragmented across borders.

Beyond territoriality, international law has also developed other recognised jurisdictional bases, including nationality and passive personality. Nationality jurisdiction allows a state to regulate the conduct of its nationals abroad, while the passive personality principle permits a state, in some circumstances, to claim jurisdiction based on the nationality of the victim. The passive personality principle can be described as a doctrine of international law under which a state may assert jurisdiction over offences committed abroad that injure its nationals (Encyclopaedia Britannica, 2024). Current discussions of nationality jurisdiction similarly recognise that states occasionally punish crimes committed overseas by their own citizens because citizenship creates a continuing legal bond (Number Analytics, 2024). These doctrines suggest that the old territorial model has already been qualified. Even without full-blown universal jurisdiction, international law accepts that states may sometimes enforce criminal law beyond their borders where there is a sufficient connecting link. That development supports a moderate answer to the question: enforcement of foreign or foreign-related criminal law is legitimate where the link is real and the legal basis is clear.

The strongest case for one country enforcing the criminal law of another arises with international crimes so grave that they are considered offences against the whole international community. Here, universal jurisdiction becomes relevant. Cassel defines universal criminal jurisdiction as the principle permitting any nation to prosecute certain serious international crimes regardless of where they were committed, by whom, against whom, or with what specific tie to the prosecuting state (Cassel, 2004). The rationale is plain: some crimes, such as genocide, torture, or war crimes, are so heinous and so likely to go unpunished by territorial states that the normal jurisdictional rules are inadequate. If the territorial state is unwilling or unable to prosecute, and if other states are barred from acting, impunity follows. In such cases, one country may not only enforce another’s criminal law or an international norm; arguably, it should do so.

That said, universal jurisdiction must not be romanticised. Yee warns that discussions of universal jurisdiction are often conceptually confused and overly expansive, and he calls for a more rigorous assessment of what truly counts as universal jurisdiction (Yee, 2013). This criticism matters because universal jurisdiction can become politically inflammatory if invoked carelessly. A state that claims power to try foreign officials for conduct with no meaningful connection to its own legal order may appear less like a neutral guardian of humanity and more like a politicised actor using criminal law to project moral or geopolitical influence. The lesson is that even the strongest departures from territoriality require discipline. Universal jurisdiction should be reserved for a narrow category of crimes recognised by international law and exercised according to strict procedural safeguards.

The International Criminal Court (ICC) offers perhaps the best institutional compromise between the demands of sovereignty and the need to prevent impunity. The Rome Statute is built around complementarity. The ICC does not replace national courts but acts when states are unwilling or unable genuinely to carry out an investigation or prosecution, and Article 17 addresses admissibility on that basis (Rome Statute of the International Criminal Court, 1998). This model is important because it preserves the basic idea that criminal law should normally be enforced by the state with primary jurisdiction, while recognising that there must be a fallback where that system collapses or is manipulated. In other words, international criminal justice does not abolish sovereignty; it conditions it. A state that refuses to prosecute atrocity crimes cannot indefinitely hide behind territorial exclusivity while victims are denied justice.

Ultimately, then, one country should enforce the criminal law of another country neither never nor always, but to a carefully defined extent. It should do so where cross-border cooperation is necessary to prevent offenders from escaping justice, where the legal basis is recognised, where the offence is serious, and where the process respects rights and legality. Extradition, mutual legal assistance, nationality-based jurisdiction and, in rare cases, universal jurisdiction are all justified because the alternative is impunity. Yet there must remain firm limits. Ordinary criminal law should still be primarily territorial. States should not become general-purpose enforcers of foreign penal policy, nor should they assist requests tainted by political persecution or fundamental unfairness. Sovereignty still matters, but in the modern world sovereignty is not best protected by refusing all cooperation. It is best protected by cooperation governed by the law.

The most convincing stance, therefore, is that one country should enforce the criminal law of another to a substantial but constrained degree. That is the only position capable of taking both sovereignty and global criminality seriously. Too little cooperation creates safe havens and rewards flight; too much invites abuse and erodes legitimacy. The proper answer lies in a middle position: enforce where justice genuinely requires it, refuse where rights or legality are compromised, and treat international cooperation not as an exception to criminal law, but as one of the conditions of making criminal law effective in an interconnected, globalised world.