Are there any legal precedents regarding the enforcement of a country&#39;s laws on its citizens abroad? I'm asking about the United States specifically but it would be valuable to hear about other countries as well. Are there legal/constitutional arguments against the application of US laws on US citizens while they are abroad? For example, marijuana is illegal by US law. Suppose an American travels to Canada where (starting next week) marijuana is legal, and smokes to his lungs' content. Can he be charged under US law for possession and consumption of an illegal substance? Would this be constitutional? There are countless similar examples. Suppose an American moves to Saudi Arabia and marries 5 wives concurrently. Can he be charged for violating polygamy laws? To summarize, does US law travel with its citizens wherever they go, or does leaving US soil remove US legal obligations?
When a country makes criminal laws, these laws usually apply to anyone present in the country, and acting in the country. But the country is free to declare that some law might apply to its own citizens in a foreign country, or even foreign citizens in a foreign country. Assuming the laws about using marijuana say nothing about the country, that most likely means it only applies to using marjuana in the country itself. But if the US government decided that taking marijuana in Canada is illegal for US citizens, then nobody can stop them. In this case, Canada would not extradite you (unless Canadian law says that it is criminal for Canadians to use marijuana in another country), and Canadian police would likely not collect evidence. So even if illegal, it would be hard to convict you. PS. The "polygamy" case would be interesting, I think you would have to read the exact wording of the laws in every country. Some countries will say that you can't get married twice, and the attempt to get married a second time while already married is bigamy. In that kind of country you wouldn't have committed a crime within that country. Also, you would only be married to the first wife.
A state's criminal jurisdiction normally applies to acts committed in that state's territory. So if you consume something in state A, you can't be charged in state B for violating state B's prohibition against consuming that thing. However, if state B has a prohibition against public intoxication, and you enter its territory while intoxicated, you could be charged for violating state B's prohibition on public intoxication. The fact that you're crossing state lines also increases the possibility that the federal government would want to get involved; the location of the federal prosecution could be in either state, although neither state's court system would be involved.
In general, yes. 1 USC 109 states that: The repeal of any statute shall not have the effect to release or extinguish any penalty, forfeiture, or liability incurred under such statute, unless the repealing Act shall so expressly provide, and such statute shall be treated as still remaining in force for the purpose of sustaining any proper action or prosecution for the enforcement of such penalty, forfeiture, or liability. Translated into plain English, this means that if you were to smoke marijuana in a Yellowstone National Park campground today, and Congress were to pass an act saying &quot;28 USC 841 is repealed&quot; tomorrow, you could still be arrested and convicted for possession of a controlled substance next week. However, if the act instead stated &quot;28 USC 841 is repealed and no retroactive prosecutions shall take place&quot;, then you can't be convicted. (The other half of 1 USC 109 is basically the same thing, applied to temporary laws: if a temporary law expires, you can still be prosecuted for actions taken while the law was in effect, unless the law states otherwise.)
I'm answering your title question and assuming that you meant to present a circumstance that would actually trigger criminal liability, but based on the ages you've actually used in your hypothetical, you may not have done so. I'll ignore that complication and just present what the law is. Yes, there are some U.S. laws that people can be found to violate while in another country. The Department of Justice has a &quot;citizen's guide&quot; explaining extraterritorial sexual exploitation of children. The main offences are: 18 U.S.C. § 2423(a): Transportation with intent to engage in criminal sexual activity 18 U.S.C. § 2423(d): Travel with intent to engage in illicit sexual conduct 18 U.S.C. § 2423(c): Engaging in illicit sexual conduct in foreign places For § 2423(a), there must be the intent to engage in &quot;any sexual activity for which any person can be charged with a criminal offense.&quot; For § 2423(b) and (c), &quot;illicit sexual conduct&quot; means, among a few other things: &quot;a sexual act (as defined in section 2246) with a person under 18 years of age that would be in violation of chapter 109A if the sexual act occurred in the special maritime and territorial jurisdiction of the United States.&quot; Chapter 109A includes § 2243(a): Whoever, in the special maritime and territorial jurisdiction of the United States or in a Federal prison, or in any prison, institution, or facility in which persons are held in custody by direction of or pursuant to a contract or agreement with the head of any Federal department or agency, knowingly engages in a sexual act with another person who (a) has attained the age of 12 years but has not attained the age of 16 years; and (b) is at least four years younger than the person so engaging; or attempts to do so, shall be fined under this title, imprisoned not more than 15 years, or both.
In the US, there are a number of non-government organizations which take on such cases, such as the ACLU or the Institute for Justice; individual law firms may also take such cases pro bono. There is no automatic right to free representation in case a constitutional issue is alleged, so if IJ doesn't like your case they won't take it. These are private organizations: there is no general government agency that one can call on, other than the Public Defender's office in case you are charged with a crime and can't afford legal defense. (A constitutional issue may arise in a case that a PD might handle, but you can't e.g. call on the public defender to sue the government for infringing your 2nd Amendment rights.) A state attorney general could file suit against the US government over a constitutional issue, as Washington's AG did in the case of the Trump travel executive order, where the underlying issues were constitutional. An individual might inspire a state AG to take on an issue, but the AG would be representing the interests of the state, broadly, and not individual interests.
Constitution of the USA, Article IV, Section 1: Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof. and the Commerce Clause (Article I, Section 8, clause 3): [The Congress shall have Power] To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes; SCOTUS has found the former to mean that states that do not allow same-sex marriages in their laws must recognize same-sex marriages registered by other states - Obergefell v. Hodges. Maybe one could argue that driver licenses are not equivalent among states, but I would expect judges (SCOTUS) to require a very well reasoned explanation. For example, maybe Alaska could refuse to recognize licenses from Florida because Florida drivers do not know how to cope with snowed roads. But even in that case Alaska probably would need to produce data showing that these measures aim to serve the public interest (avoid accidents) and that there are no other ways of getting the same result. OTOH the Commerce Clause has been successfully used to avoid states mandating racial segregation of travellers, so it is quite reasonable to see it being used to prevent a state from trying to limit the mobility of citizens from other states (again, in the supposition that the state restricting it cannot show a compelling reason to do so). AFAIK, only the Federal Government could invoke the Commerce Clause; I would expect a lot more people (in your example, the PA government or maybe even any PA driver) would have standing.
All countries (and some sub-national jurisdictions) have extraterritorial jurisdiction The U.S. Criminal Code asserts the following items to fall within the special maritime and territorial jurisdiction of the United States, much of which is extraterritorial in nature: The high seas and any other waters within the admiralty and maritime jurisdiction of the United States and out of the jurisdiction of any particular state, including any vessels owned by US persons that are travelling on them Any US vessel travelling on the Great Lakes, connecting waters or the Saint Lawrence River (where that river forms part of the Canada–United States border) Any lands reserved or acquired for the use of the United States, and under the exclusive or concurrent jurisdiction thereof Any island claimed under the Guano Islands Act Any US aircraft flying over waters in the same manner as US vessels Any US spacecraft when in flight Any place outside the jurisdiction of any nation with respect to an offense by or against a national of the United States Any foreign vessel during a voyage having a scheduled departure from or arrival in the United States with respect to an offense committed by or against a national of the United States Offenses committed by or against a national of the United States in diplomatic missions, consulates, military and other missions, together with related residences, outside the US International Parental Kidnapping Crime Act The US is actually pretty narrow in its assertion of extraterritorial jurisdiction and the Supreme Court has held that there is a presumption against extraterritoriality. So US laws have to explicitly assert a claim of extraterritoriality. Contrast this with, say, France where the Code pénal asserts general jurisdiction over crimes by, or against, the country's citizens, no matter where they may have occurred. Crimes perpetrated from foreign jurisdictions Notwithstanding, a crime can be perpetrated in a country without the perpetrator ever having been in that country. Hacking of computer systems is an obvious example. However, almost all criminal codes include a crime similar to &quot;Attempted X&quot; or &quot;Conspiracy to commit X&quot; which clearly don't require a physical presence. Terrorist attacks are often planned in third-party countries by a group, only a small number of whom actually go the country to commit the actual attack but all of them have committed a crime under that county's jurisdiction. Extradition Any country (A) may request extradition from any other country (B) where A asserts that it has a case to bring against the individual. No country can demand extradition. B will decide whether to grant the request subject to its own law on the matter and the provisions of any extradition treaty that may be in place between A and B. Dual Criminality A crime committed in country A may engage the jurisdiction country B. If so, country A gets first crack at prosecution. Country A might decide not to prosecute, might prosecute and fail or might prosecute and succeed. Notwithstanding the outcome country B can decide to prosecute as well. Usually if the defendant has been prosecuted by country A (win or lose), country B will not prosecute. A specific example An Australian engages in sex with a French-American child in the US embassy in Rome, Italy. Italy has jurisdiction because the crime was committed in Italy. The US has jurisdiction because the offence was committed against a US national in a US diplomatic mission. France has jurisdiction because the victim was French. Australia has jurisdiction because sex crimes against minors by Australians are prosecutable in Australia. The perpetrator flees to the UK (with whom all four countries have extradition treaties) where they are arrested - the UK government (courts and foreign minister) will decide if and to whom the perpetrator will be extradited (probably Italy). After they are prosecuted there (and serve any sentence) any of the other three may request extradition. And so on.
Scenario 1. It doesn’t matter what it says. If it was not legally ratified, it is not legally in force. There is no absolutely no paradox at all. It is essentially just a draft amendment and would be thrown out if any attempt was made to enforce it and challenged.