We are now finishing Article I of the Constitution. All of this article so far has had to do with the Legislature. Section 10, takes a turn to address limitations placed on the states. Logically this is a seperate Article altogether, but the founders apparently decided to just stick it here. While short and to the point, most of the limitations require either a definition or some other type of explanation.
Right off the bat, we have "No state shall enter into any Treaty, Alliance or Confederation. How does that match with the numerous agreements California has with other trading partners, most of whom are entire countries? The answer is that California must work hard not to run over the line of US sovereignty. The documents California signs are ofter characterized as Memorandum of Understanding. They are non-binding and represent the intent of both parties to work together towards a common goal. It is clear that tariff rates, for example, are set by the federal government, independent of any goals California may have set themselves. While the distinction between Treaty, Alliance or Confederation, and Memorandum of Understanding, may be blurred, there has been no Constitutional issue as yet brought against California by the federal government.
Letters of Marque and Reprisal are agreements made with private citizens allowing them to arm their own ships and use them to attack enemy ships. Such arrangements were used by the federal government during both the Revolutionary War and the war of 1812. While not used since, the founders chose NOT to include them in the powers forbidden to Congress. Elon Musk has built his own space program, maybe he would like to build his own Navy as well?
Coin money is pretty clear, once you understand that coin is being used as a verb. In 1787, the predominant form of money was the Spanish piece of eight. The federal government expected to mint our own coin and did not want the states getting into the act as well.
Bills of Credit, issued by a government are basically paper money. Most of the colonies had experimented with that prior to the Revolutionary war, and the Continental Congress used them as well. Experience was universally bad, with paper money all quickly devaluing to only a fraction of its original value. So this prohibition made sense. Just don't go there.
Only gold and silver coins can be legal tender. This is an extention of the above. Not only are you prohibited from issuing any money of your own, but you are forbidden to use anyones paper money as your legal tender.
A Bill of Attainder is a legislative act which declares a person or group to be guilty of a crime, and imposes a punishment without a judicial trial.
An ex post facto law is one that retroactively changes the legal consequences of an act committed prior to the enactment of the law. For example, supposing that today, August 14, you trespass over the local railroad property. Suppose further that such act is currently punishable by a fine of $100. Now suppose further that on September 1 the fine is increased to $200, to be retroactive until August 1, and at your court hearing on September 2, the judge charges you the $200. That would be an ex post facto law and it would be disallowed by this statement in the Constitution. The judge would only be allowed to fine you the $100 which was what the fine was as of the date on which you committed the act.
An example of impairing the obligation of Contracts would be a law that said the rent owed under any existing rental agreement would be automatically reduced for the balance of its term by 10% per month.
A title of nobility would be something like Count, or Duke.
When considering the final two paragraphs of this section, note that the prohibitions here can be lifted with the consent of Congress. This differs from everything prior, which are absolute prohibitions.
The paragraph on Imposts and Duties is an attempt to allow states to collect their costs of things like agricultural inspections without running afoul of the constitutional prohibition against the charging of tariffs between states.
The final paragraph is a hodge podge of items requiring the consent of Congress. Duty of Tonnage is a fee for using a harbor. Congress does not want the states getting into competition between themselves with regard to attracting maritime trade. Troops, ships, and engaging in war are all simply the idea that we have become one country, and our defense is not something we are going to go about one state at a time. And Agreements and Compacts take us back to the beginning with the acknowledgement that some kinds of documents, Agreements and Compacts for example, just require an OK from Congress, while others, Treaties, Alliances and Confederations, are outlawed altogether.