Since the UN charter is amendable easily. What is stopping nations from amending it to have less UN obligations? It seems like a pretty intuitive thing to do. They could even invalidate various treaties they have signed.
The UN charter is really hard to amend It requires approval by two-thirds of its member states, and ratification by two-thirds of its member states, including in both cases by the five permanent members of the security council (the USA, the UK, Russia, China, and France). It's happened a total of 3 times, in each case, for completely non-controversial reasons.
This is a hard question, but a good question. The following relates to the issue from the perspective of the USA. You ask "...if the US wants to invade France, can they officially declare war by...", You have to make clear what you mean by "can". If you mean whether or not the US has the physical ability to do this, then of course they do. If you mean whether they are allowed, then this is another question. When you ask whether something is allowed, then you have to make reference to a moral code or a law that determines what is and what isn't allowed (legal). Normally each country will have laws that govern what is and what isn't legal for it's citizens to do. That hard part is how this applies to nations. There are two sides to the question. (1) What are the leaders allowed to do under their own laws, (the domestic laws) (2) what are countries as entities allowed to do? (the international laws) It sounds a bit like you are asking about the second thing. Here treaties govern what is and what isn't "legal". However, usually when someone breaks a law, other entities have the power to enforce that law and decide (judge) whether the person has broken the law. The question is: who decides whether a country has broken a treaty or an international law? And if a law is broken, what exactly can be done about it? This is hard to answer. Consider for example the conflict in Ukraine. Here many will argue that Russia has piratically invaded Ukraine. There should be war between the nations. But Russia denies this and other world powers have done little beyond imposing sanctions. This illustrates how hard it is to deal with this question. One question that comes up is what the purpose of international treaties are if a country can just violate them without much consequence. Pointing out two points about this. (1) If, for example, a president wants to convince his/her own congress that the country should engage in war, then it makes a stronger point if you can show how the country you want to engage has violated international trities. (2) After you have won a war, you might want to prosecute the leaders of the loosing power. Here you will stand stronger if you can make references to some international law that existed before the conflict started. This second point is illustrated in the Nuremberg principles. Here it was exactly stated that "Any person who commits an act which constitutes a crime under international law is responsible therefore and liable to punishment." According to the US constitution "Congress shall have power to ... declare War". That means that historically Congress has the power to decide where to wage war. The War Powers Resolution says, for example, that "The President in every possible instance shall consult with Congress before introducing United States Armed Forces into hostilities ...". Note that this doesn't mean that the US has do formally declare war before going to war. Example: The Iraq War was authorized by Congress, but there never was a formal declaration of war. It is interesting that you ask about the timing for when the declaration should be given. The Japanese wanted to deliver their declaration of war just before the attack on Pearl Harbor. But because of issues with decrypting the message from Japan to the Japanese Embassy, the declaration wasn't delivered until after the attack. Remember also in all of this that the winning party to a conflict, usually decides what was and wasn't legal! One good reference for more on all of this is the report by the Congressional Research Service called "Declarations of War and Authorizations for the Use of Military Force: Historical Background and Legal Implications". Here you can see more on what I have tried (and failed?) to say above.
It can (and has) been argued that some of the post-bellum trials of Germans and Japanese (but no Italians because they were Allies now) proceeded on shaky legal grounds. However, the arguments of your friend are wrong. In addition, many of the cases proceeded on solid legal foundations based on war crimes (e.g. the Commando Order) and treatment of prisoners-of-war (e.g. the Stalag-Luft III murders). Citizens and non-citizens are protected by the law and were even in Nazi Germany, albeit not equally. The Nuremberg Laws did not classify Jews as non-humans, merely as non-citizens (which is not to trivialise their awfulness). Superior orders has never been a recognised defence for criminal acts under civil or common law. The first recorded rejection of this defence was in the trial of Peter von Hagenbach in 1474. The roots of modern International Law can be traced to the 16th century and were definitely well advanced by the 19th, let alone the mid-20th. Nations accepted that international treaties and diplomacy were supported by international law and these included the Geneva Conventions of 1864, 1906 and 1929, since updated in 1949 (of which Germany was a signatory) among many others. In addition, since the Enabling Act (which instituted Hitler's dictatorship) was quite probably illegal, it can be reasonably argued that all actions that flowed from it (i.e. basically everything that the Nazi's were tried for) was illegal under German law.
It sounds to me like the parties made proposals with an intent to draw them up and formalize them but didn't intend to form binding agreements. The first agreement sounds vague. The second was committed to writing, suggesting that the written deal was to be the real agreement, and not executed. In the last case, it doesn't appear that there was an agreement because there was no meeting of the minds on the essential term, which was the price. Going to court is expensive. It is expensive whether this is litigating underlying disputes or trying to enforce an alleged oral settlement that is disputed. Also, settlement discussions that don't result in a resolution are not admissible as evidence in court. Making a deal would be nice, but Dave's concept of what constitutes a deal seems to be out of touch with reality.
At the time of annexation of country X someone would have to decide the status of the countries citizens: If all citizens of X are now citizens of the USA, and whether they are legally citizens from the date of annexation or since they were citizens of X, and if they are considered residents in the USA since the day they became residents of X, and if they are retrospectively "born in the USA" if they were born in X. And other things, like whether non-citizen legal residents of X are now non-citizen legal residents of the USA. That has to be decided for many reasons, and the answer to your question follows naturally from this. Maybe you could check on a history site if anyone knows how this worked with Hawaii.
No Recognition of territorial claims is the sole province of the diplomatic branches of national government, and of heads of state. In the US it is the State Department, and ultimately the President. The actions of telephone operators and people engaging in other forms of communication cannot and do not bind the decisions of the President, or of other heads of state. Besides, there may be cases in which a telephone country code or a web domain may not match the actual, undisputed legal status of a territory. Accepting a phone call does not affect a country's legal status. For decades the US did not recognize the communist regime in China. Legally, it considered that the Republic of China (aka Taiwan) was the only valid government, and the acceptance of telephone calls did not change that.
You are indeed thinking of the Vienna Convention on Diplomatic Relations of 1961. This codified a portion of existing customary international law on diplomatic immunity. It is the result of several years of legal negotiations at establishing a common set of rules that would be generally acceptable. The basic concept of immunity for ambassadors is very ancient, and there is still a body of customary international law that was not codified. For example, the 1961 Convention only deals with permanent missions, not temporary ones like for multinational summits. The history and practice are also helpful for interpreting the Convention itself, such as when considering the scope of diplomatic duties which are protected, as opposed to extracurricular activities which might not be. In the UK, the Convention is implemented by the Diplomatic Privileges Act 1964. This mostly repeats the relevant parts of the Convention text, in Schedule 1, and also includes sections integrating those provisions with domestic law. As far as the courts, section 4 says that If in any proceedings any question arises whether or not any person is entitled to any privilege or immunity under this Act a certificate issued by or under the authority of the Secretary of State stating any fact relating to that question shall be conclusive evidence of that fact. This means that what happens procedurally in a UK court is that someone wanting to claim immunity must come with a letter from the Foreign Secretary attesting that they are a real diplomat and not just making it up. The court then considers, from that fact, what legal consequences follow, depending on the type of diplomat involved (e.g. heads of mission have broader protection), the nature of the case (criminal case where the diplomat is accused? civil case where they are the respondent?), etc. That is a matter of interpreting the Convention, plus maybe customary international law - it doesn't mean the diplomat gets to wave their certificate and end the proceedings. The purpose of section 4 is to avoid the court entering its own fact-finding process about whether someone is a real diplomat. That is felt to run the risk of the court causing diplomatic offence by accident - consider Israel and Palestine and China and Taiwan for potential pitfalls. The doctrine of &quot;one voice&quot; obliges the courts to follow the executive's lead. Prior to the Act of 1964, diplomatic immunity was covered by several other enactments, but with the same basic model for implementing immunities in court. There were different regimes for Commonwealth countries and others, which is not the case any more. The first such Act was passed in 1708 after an embarrassing situation with the then ambassador from Russia, who was imprisoned for his debts, angering the Tsar. In general, domestic courts in the UK can take account of customary international law if it is relevant. They can also look at treaty texts, even ones the UK has not signed, to help interpret international law. (In the same way, they can look at academic articles, travaux préparatoires, etc., which have no formal status as law.) If the UK signed the 1961 Convention but did not pass the 1964 Act, then courts might be able to treat the Convention as &quot;background&quot; - but would still be bound by the 1708-1955 Acts on the topic, as far as the actual procedure and rules to follow. A diplomat would not be able to avail themselves of their specific 1961 rights, unless perhaps there was some gap or ambiguity in the domestic law where they could squeeze in an argument that the Convention supplied the proper interpretation of whichever point of customary international law was involved.
The most commonly used definition for statehood is the declaratory theory, codified by the Montevideo Convention. This says that statehood doesn't depend on recognition by other states; it merely requires four things: A defined territory A permanent population An effective government The capacity to enter into relations with other states. You immediately run into issues around the defined territory (you don't really have one) and the capacity to enter into relations with other states. But let's ignore those for a second. Meeting these requirements in some abstract world doesn't mean you get treated like a state. If no one else agrees with your claim to statehood and they act inconsistently with it, you have little recourse. You might get them not caring enough to do anything about it, but if they decide you're not a country you're out of luck. You have some misconceptions about statehood as well. A country is allowed to forbid trade with any foreign country, even ones it recognizes as sovereign states. See: US embargo on Cuba. It is also entitled to deny foreign ships access to its ports. Ships flying the flag of a sovereign state are entitled to innocent passage through territorial waters of another state, but not to the use of that state's ports. A country can certainly allow people to be killed and still be a country. See: the US, which has the death penalty for certain crimes. But if you're killing nationals of a foreign country, that foreign country is likely to take a keen interest in your activities. If the killings are judicially-ordered executions based on violations of your penal laws, that's one thing -- Australia might consider it awful that an Australian citizen was shot by Indonesia for drug smuggling, but they recognize that Indonesia is a real country with its own laws that it has a right to apply. If it's just lawless there, the keen interest might culminate in a travel warning. But in more extreme cases, or where the killings are of people who didn't willingly enter your territory, you're looking at potential military action.