Just out of curiosity, which set of laws would be used if you committed a crime across a border?

For example, suppose I were standing on the American side of the America-Canada border. If I were to shoot and kill someone on the Canadian side, which country's laws would be followed?

  • For which crime? Commented Mar 29, 2016 at 17:58

3 Answers 3


The US has jurisdiction because you committed a crime in the US. Canada has jurisdiction because you committed a crime in Canada.

As added complications, if you are a Mexican citizen then Mexico has jurisdiction and if your victim is Chinese then China has jurisdiction. If you get arrested on an Interpol warrant in Spain then Spain has jurisdiction. And so on ...

Your implicit assumption is that jurisdiction is exclusive, it isn't. Any country (or sub-national jurisdiction) that claims jurisdiction has jurisdiction, at least to the extent of testing that claim. Whether any given polity has jurisdiction depends on the particular law involved, some laws are only applicable within that countries borders others are extra-territorial, some are applicable to citizens but not non-citizens or vice-versa, etc.

  • 1
    Pretty much this. Countries will look for excuses to prosecute anybody they can. The United States often prosecutes people who commit crimes on the high seas or in foreign countries with no other reason than they are American citizens. It is not unusual for American courts to claim they can prosecute any American citizen anywhere in the world for breaking US laws even though the person is not in the United States.
    – Cicero
    Commented Mar 29, 2016 at 22:09
  • @Cicero Its more than a claim - they definitely can.
    – Dale M
    Commented Mar 30, 2016 at 21:32
  • @Cicero the US can also disclaim jurisdiction when a federal officer shoots across the Mexican border and kills a Mexican teenager.
    – phoog
    Commented Apr 2, 2016 at 15:36
  • +1, especially with Canada, if you're a Canadian citizen you can be charged for committing an act that is deemed criminal at home, even if the place where you committed the act was legal.
    – user900
    Commented Apr 4, 2016 at 20:18
  • 1
    @Trevor federal states can be bound by federal precedent - that would settle the law for that country. Sovereign states would need to settle the law for themselves - hopefully this would result in one of them taking the ball and running with it, but maybe not.
    – Dale M
    Commented Nov 15, 2017 at 7:39

In short, the laws of whichever country decided to prosecute you.
All of the overt acts that you committed for this crime were in the US (let's assume that's the case, anyway) and the US clearly has jurisdiction over the place where you were standing, so the US could prosecute you for this. Canada might also have jurisdiction because the effects of what you did occurred in Canada.

  • 1
    What if it was the other way round - someone on the Canadian side of the border shooting someone in the USA? If Canada said "we think the USA has jurisdiction" and the USA said "we think Canada has jurisdiction", would that murderer go free?
    – gnasher729
    Commented Mar 29, 2016 at 23:27
  • 1
    Each side can believe the other to have jurisdiction whether or not it believes itself to have jurisdiction. In this situation it is most likely that both countries have jurisdiction to prosecute, but the country where the offender is physically located is the one that has jurisdiction to make the arrest, and in this situation the one who arrests is also the most likely one to prosecute.
    – Burned
    Commented Mar 30, 2016 at 3:41
  • I really meant a situation where the US law says that Canada should have jurisdiction and the USA hasn't, and the Canadian law says that the USA should have jurisdiction and Canada hasn't. So no side would feel responsible. For example if the US law says "the country from which the shot was fired, and no other country" and Canadian law says "the country where the victim is hit, and no other country" and each country's law says that it isn't their business.
    – gnasher729
    Commented Mar 30, 2016 at 15:49
  • @gnasher729 it would be a rather unusual situation. The criteria for criminal jurisdiction are usually recognized by every country as part of the so-called customary international law. However, should this issue arise, I suspect that, in their own interest, US and Canada would agree to submit the case to the International Court of Justice.
    – A. Darwin
    Commented Mar 30, 2016 at 16:12
  • @gnasher729 can you give examples of one country's laws saying that another has jurisdiction and they themselves do not? Each country can decide, on its own, whether or not they have jurisdiction, and if they believe they can prosecute a person & want to do so but don't have territorial jurisdiction to arrest the person, they can ask the local authorities where the person is to arrest and extradite (who might comply or not, depending in large part on what the local authorities think of the crime and the presence of an extradition treaty).
    – Burned
    Commented Mar 31, 2016 at 0:26

As said elsewhere both countries have jurisdiction (can prosecute the accused within the limits of their laws).

What would actually happen would depend upon several factors, the most important being not where the crime was committed, but who apprehended the accused. One country might try for extradition, the other may or may not agree to it. Montana has the death penalty, if the crime was committed there by a Canadian citizen, they might want to take custody in order to avoid having their citizen killed by another country.

Double jeopardy may or may not apply depending upon the law of the country claiming jurisdiction (for instance if our hypothetical killer was Iranian, he could serve his time in either the US or Canada and still be re-prosecuted in Iran).

Basically international law exists only as a voluntary amendment/adoption to a countries laws, and so there is no defitive statement that can be made without describing the exact circumstances. For instance if the crime had been drug dealing with the money and drugs being tossed across the border, our Iranian subject wouldn’t have had to worry about re-prosecution as Iran law would have been satisfied with his conviction and punishment by either.

But it’s a nigh universal fact that you can’t imprison someone that is beyond your reach, so...it do nes upon whee you are.

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