San Remo Manual on International Law Applicable to Armed Conflicts at Sea: International Institute of Humanitarian Law Book

De Jure Belli ac Pacis means On the Justice of War and Peace in Greek. This is a kinda weird book, as far as books go, but pretty worthwhile in the end. The plot starts out real slow at first, and the characters are distant and hard to relate to. You really have to get used to Grotius' style, which is a little outdated because he was a Roman, and he references tons of Roman and other examples to bolster his arguments, sometimes even like 20 pages of examples, and by the end, you're like, OK I get it dude, Jesus said it was ok to have wars, or whatever. This book is really long, but I feel like in olden times, people maybe just wrote longer books, and you have to be patient about that because they say a lot of good stuff when you give them a chance.

Grotius' main point is that there is a natural law in the world which governs even how countries have wars with each other, even though while they're having the war, it seems like they might not be governed by any laws at all, so many people have argued that there is no such law. But this natural law is not based on God or anything subjective or controversial like that (although God is cool with it). It's based on two things: the universally observable human impulse to defend himselves when he is under attack, and the equally universal fact that humans are sociable and want to live together. The first part justifies why war is justified in the first place, because we have a right to defend ourselves when we're attacked. But the second is really cool, because it limits the extent to which we can do the first part, so that we can't just do whatever we want in self-defense, like Mr. Tom Hobbes says thousands of years later, but we can only defend ourself to the degree that our defense promotes sociability, or maintains our society as a whole. That still means we can do a lot of badass stuff in war though.

I'm not sure if I buy Grotius ultimately, because it's really hard to make countries follow laws when they are in wars and there is no way to hold them to the laws, or they feel existential about a particular war and conclude that they have to do whatever it takes to win it or be totally crushed, like what happened to the land of Carthage in Grotius' time. But for the most part, I feel like Grotius is really good to read when you get tired of some of the edgier authors in this genre like Bodin and Hobbes, because he has a more moderate idea about what a country's self-interest is, and thinks that laws about contract and property can be extrapolated from within a country to govern relations among countries. Especially for people who care about international law and human rights nowadays, it's really important for them to justify that without relying on different subjective religions, and if you think that Grotius' justifications are not that good, you need to think about whether you have any better ones.