How Does the Compulsoriness of Skipper Licences and Flag State Relate?

Question

Focused core question

What documents/licences should I get, if any, in case I didn't wanted to have problems with authorities while sailing around the world, on any given type of sailboat having any kind of flag state?

Corollary questions and context to help you think about the nuances while answering

Let's suppose you want to buy a yacht and you don't want to have problems with authorities that stop you while sailing around the world. Let's also suppose that you are from country A, and that you are looking into possible yachts deals from countries A, B and C. What kind of skipper licence would you need to have if any? According to my research, when you are on a vessel that has a state flag from country A, you are under the law of country A. Does that mean that I need to have a skipper licence from country A?

1. What if I change flag state?
2. What if you want to buy a boat from country B or C?
3. How will country A be able to enforce its law on what happens on your yacht with state flag A, if you are on the other side of the world, in the waters of another country or in international waters?
4. Can I have no flag state and be able to not have any law mandated over me? If so, how do things work in that case?
5. How does the International Certificate of Competence (ICC) plays into all this? Can it be used in place of a skipper licence? Does it provide any advantage to have it?
6. If it is true that a yacht with state flag from country A must follow the law of country A, can country B require you to have an ICC for example, when sailing in their waters? If so, how? Moreover, how does the boundry between the laws of country A and country B work when they are in contrast for example?

Answer 1

Let's start with the usual rule in international law: if the law enforcement of country X arrests you and claims their laws apply, you are 0-1 behind. You may claim that (only) the laws of country A apply, but that argument tends to hold little value in the eyes of country X.

Now, if you're a citizen of country A flying the flag of A and holding the licenses required by A, you have a decent chance of getting at least a sympathetic ear of the ambassador. Still, if you refused a pilot and rammed an oil tanker into the main port of country X, that's not going to help you much. Obeying the laws of country A in addition to those of country X is a good idea, because you want that ambassador to be on your side.

As you mention in your question, there's a whole lot you can do to make things more complex. That is missing the point, really. As a citizen of country A, you want to make it clear to the law enforcement agencies of other countries that they're dealing with a citizen of A. In international waters, that means they better have a good reason to board you, let alone detain you.

Now, the ICC you mention is chiefly a European thing, and European countries are generally pretty friendly towards each other. As noted, you want to avoid getting into discussions with law enforcement about petty details. The ICC helps because country X.eu is more likely to recognize the ICC than the skippers license of A.

Finally, you talk about the "boundary" of the laws of A and B. Laws overlap a lot more than geographies. If there's an unresolvable conflict between the two laws, you better avoid getting into the contested area altogether. But the usual overlap is benign; you just have to follow all rules.