The law of nations forms only half of international law. There is a large and ever developing part that applies to individuals. Human rights form the core of this law, but there are many other provisions that specifically relate to individuals. In the Nap era this was much less developed, but the law of nations side of things itself has significant implications for individuals. International conventions on how a state may treat civilians - be they their own subjects or those of another country - naturally have consequences for all sorts of people. If there is a convention stating that civilians in a hostile country must not be ill-treated, this is good for them. But if there is one that allows for harsh measures, this obviously will have bad repercussions for them. The problem I was alluding to was that in some cases international conventions are formed and dominated by a few powerful states, but whose implications will be far-reaching.
So to return to my original example it was deemed to be perfectly acceptable to crush a rebellion by one's own subjects, and to punish severely those who undertook such activities. This was a convenient custom for the powerful governments of the time, but obviously a problematic one for the many people who were ruled or threatened by foreign powers. To take another example the British were adamant about naval rights being recognised and respected because they were the prime beneficiaries of such provisions, sometimes to the detriment of other powers and people. As such any claim to a widespread recognition and acceptance of the just and moral nature of international law as a whole is compromised by its tendency to be shaped by particular interests, whose views are often not accepted or of benefit to the majority.
Regards,
Chris