How does universal jurisdiction allow national courts to prosecute war crimes committed outside their own country?

Under international law, the principle of universal jurisdiction allows national courts to prosecute specific, grave offenses—such as war crimes, genocide, and torture—regardless of where the crimes were committed or the nationality of the offenders or victims.123

While states typically exercise jurisdiction only over crimes occurring within their territory or involving their own nationals, this rule is relaxed for international crimes that are considered offenses against all of humanity. Because these acts are viewed as having no particular geographic location, any state that gains custody of an alleged perpetrator may assert the authority to try them.234

In some instances, international treaties mandate this process through the principle of aut dedere aut judicare ("either adjudicate or extradite"), which requires national governments to either prosecute the offender themselves or extradite them to a country prepared to do so. This framework ensures that individuals responsible for the most serious violations of the laws of war cannot evade justice simply by crossing borders.24