Could a new US constitution be ratified by an absolute popular vote? It is well known that the US constitution is very hard to amend, and that topics with a good overall popular approval are impossible to get in the constitution, like abortion or gay marriage. I am French, a culture where constitutions come and go, based on the principle that whatever is voted on by a referendum becomes the law of the land, and overrides anything it needs to. Could such a thing be done in the USA, or are things such as abortion or as many senators for Wyoming and California settled forever? In other words, is there principles of law more important than the current constitution, such as the right of self-determination ?
There are two ways to change a constitution: Through amendments to the current constitution. By starting a new constitution. When you start a new constitutional process from scratch, its legitimacy will not depend on the provisions of the old constitution. This process will develop outside the framework established by existing laws. You could say that the constitution is self-affirming: its legitimacy cannot come from any law because there are no laws higher than the constitution. From that point on everything could be (theoretically) possible as a way to legitimate the new constitution: a referendum (in the multiple varieties that it could be present), approval by an assembly, military intervention... The success or not of a new constitution would depend on the forces that support and oppose it.
Let's look at the Ur-example of a free-speech law, and the most wide-ranging, the First Amendment to the Constitution of the United States of America. It says (my emphasis): Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances. This limitation applies only to the government. Indeed, it has been argued that this limitation only applies to the legislative branch of government and not to the executive (except when exercising legislatively delegated power) or judicial branches. Certainly, the courts have held that it is within their power to issue "gag" restraining orders. Notwithstanding, it imposes no restrictions on how non-government actors can limit your free speech. The owner of a shopping centre can require you not to evangelise, the owner of a stadium can require you not to use offensive language and the owner of a social media platform can restrict your speech in any way they wish. You have a right to talk - they have a right not to give you a platform.
The details depend on the state, of course. The common law thing you are looking for is a writ of mandamus -- a court order to a public official to do something (or not do something) that they are required to do under the law. Writs of mandamus were traditionally only applicable to ministerial tasks (i.e. things that are basically paper-shuffling where there is little to no discretion); marriage licenses are typically considered ministerial. With discretionary actions, things are much more complicated because the government official is supposed to have significant ability to decide what should and shouldn't be allowed; mandamus doesn't apply unless there's a right to the action requested. In some cases, mandamus has been replaced with other forms of judicial review, but in Alabama it is definitely still mandamus that's involved (source: mandamus is what's previously been used to stop issuance of licenses). For federal review, which is more likely to get somewhere, the approach to use is the exact same thing that led to DeBoer (the case bundled into Obergefell that was about granting licenses), and Perry, and many of the other gay marriage cases: a lawsuit seeking an injunction or declaratory relief under 42 USC 1983, which allows actions in law and equity whenever anyone denies civil rights to a US citizen (or someone in the jurisdiction of the US) under color of law. The ultimate result of this kind of suit is a federal court order to issue a marriage license, or a declaration that it's illegal to not issue the license (and so anyone who doesn't will be subject to a court order). Violating this order, like any court order, is contempt of court.
There are certain requirements of Statehood according to the Montevideo Convention on Statehood of 1933, which is just a codification of international customary law: a permanent population; a defined territory; government; and capacity to enter into relations with the other states. Is it "legal" to buy a piece of land and claim it to be another country than before(either inventing a new one or migrating it to an already existing one)? According to international law, it is. Sure. But just because you say something is the case, doesn't mean it is. Always. Sometimes it is. But for present purposes, let's say that if you found an uninhabited island and said that you were a country, that wouldn't be the case - nor if you bought it from a man living on it. If you found some land that belonged to another country and decided to claim it as that of an existing country, then it would depend on the specific circumstances. That's exactly what happened to the Krim island in the Ukraine(now Russia maybe?), right? I don't think so. As far as I know, the annexation of territory isn't considered sale. In any case, the ownership of this land is still under dispute. So, if it's possible without the influence of these international institutions, trying this in an area with their influence would be easier, right? If trying this means declaring some land you have purchased to be a new sovereign state Nope. You probably still don't meet the requirements for statehood. If trying this means the acquisition of some land by an existing sovereign state Maybe. Probably not. The Montevideo Convention requires that statehood not be gained through force; while member states' interests may be greater where they are more invested, the requirements for acquisition of territory are the same no matter where you are. What would prevent me from creating my own nation? Money, defensibility, recognition, the fact that you probably don't own any land that you "buy" (depending on the jurisdiction and real estate system), the fact that you generally can't unilaterally declare yourself a sovereign state.
Not in US courts. It would be more accurate to say the UDHR overrides nothing and is not US law. It is a nonbinding UN General Assembly resolution; while it is very powerful persuasive authority and much is customary international law, it is persuasive authority only. See Sosa v. Alvarez-Machain, 542 U.S. 692. The US has ratified the International Convention on Civil and Political Rights, which unlike the UDHR is a treaty, meaning that is a legal obligation for the US. However, the ratification was subject to many reservations and declarations, whose net effect is that the ICCPR is not in and of itself enforceable in US courts. The US considers the US Constitution to provide the rights in question, and basically assumes no further obligations. Even if it was possible to enforce the ICCPR in US court directly, Reid v. Covert established that the Constitution overrides treaties in US court. While as a matter of international law treaties override domestic law, this is not necessarily enforceable in domestic court.
No. The Fourteenth Amendment says: nor shall any state deprive any person of life, liberty, or property, without due process of law; The Supreme Court has determined that this clause incorporates much of the Bill of Rights. The logic is mildly tortured, but it's basically that "due process of law" means "due process of a law that is compatible with the fundamental rights of a free society." This logic is known as "substantive due process," because it reads in to "due process of law" requirements about what those laws can do (as opposed to procedural due process, which is about the actual procedures being used). It's pretty settled that the Bill of Rights, after the 14th Amendment, should apply to the states. There's another possible way to get there: the 14th Amendment says "No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States," which Justice Thomas recently thought meant that the Second Amendment applies to the states in a concurring opinion. But as of now, substantive due process is the standard logic for it. Virtually all of the Bill of Rights is incorporated against the states. There are a couple things which aren't (like juries in lawsuits, and grand juries), but the Establisment Clause is incorporated (see Everson v. Board of Education, 330 US 1).
I know of no specific provision of the Constitution that would forbid it. I know of no court case in which it has been found unconstitutional. There's no "irony" clause in the Constitution. Taxation without representation may have been a grievance, but there's no inherent reason why the framers would have had to forbid it. US citizens do still have the "freedom to expatriate" (and avoid taxation) if they renounce their citizenship. There are already other examples of "taxation without representation" in US law (e.g. District of Columbia), which also have not been found unconstitutional in court, as far as I know. In many cases, expatriates can still vote for federal offices, including Congress (e.g. in a state where they used to live, or where a parent used to live). See https://www.fvap.gov/citizen-voter/registration-ballots. The Sixteenth Amendment gives Congress the power to "lay and collect taxes" with few limitations. There is certainly no explicit exception for expatriates. As far as I can tell, it would be constitutional if Congress were to impose an income tax on everybody in the world, regardless of residency or citizenship; it would just be hard to enforce.
Any court from a municipal traffic court on up can declare a law unconstitutional and the U.S. Supreme Court is almost never the court that does so in the first instance. Also, while the jurisdiction stripping law that you suggest might be unconstitutional, it is not obviously unconstitutional. The relevant language is in Article III, Section 2 of the United States Constitution (this has been modified by the 11th Amendment in ways that are not pertinent to the issue at hand): The judicial Power shall extend to all Cases, in Law and Equity, arising under this Constitution, the Laws of the United States, and Treaties made, or which shall be made, under their Authority;--to all Cases affecting Ambassadors, other public Ministers and Consuls;--to all Cases of admiralty and maritime Jurisdiction;--to Controversies to which the United States shall be a Party;-- to Controversies between two or more States;--between a State and Citizens of another State;--between Citizens of different States;--between Citizens of the same State claiming Lands under Grants of different States, and between a State, or the Citizens thereof, and foreign States, Citizens or Subjects. In all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party, the supreme Court shall have original Jurisdiction. In all the other Cases before mentioned, the supreme Court shall have appellate Jurisdiction, both as to Law and Fact, with such Exceptions, and under such Regulations as the Congress shall make. The key language being the language in bold, who scope and limitations are the subject of hot debate in legal scholarship. For example, both military tribunal law for non-soldiers and the collateral review of death sentences implicate this provision. An issue related to U.S. Supreme Court jurisdiction over military court-martial court composition will be heard this year in oral argument before the U.S. Supreme Court. There is also debate over whether the jurisdiction of every single federal court can be removed from a matter within the judicial power of the United States. In that regard, keep in mind that the United States federal court system did not have direct appeals of criminal convictions at all until the 1890s, although you could challenge, for example, the jurisdiction of a criminal court over your case with a writ of habeas corpus which is a collateral attack on a conviction in a separate civil lawsuit formally directed at your prison warden. That being said, as far as I know, a law is considered in effect until declared unconstitutional. It is illegal to break an unconstitutional law, until declared so. You are wrong. A law that is unconstitutional on its face is, in terms of legal theory, unconstitutional immediately upon enactment and a court simply acknowledges that fact. It is not illegal to break an unconstitutional law even if no court has yet declared it to be unconstitutional (in U.S. jurisprudence). A law that is unconstitutional as applied is unconstitutional in application at the moment it is applied unconstitutionally, and again, a court merely acknowledges that fact.