Henrik Syse says that the main theory of global ethics and international justice in western tradition is the natural-law tradition which goes back to beyond written record. It has been organized and identifiable teaching within our culture since Latin times of Middle Stoa and Cicero and the early Christian philosophers Ambrose and Augustine. He states "This early natural-law theorizing teaching centered around the idea of a ius naturale, i.e., a system of right which is natural and as such common to all people, available to humankind as a measuring stick of right and wrong."

Marion Young states that "A widely accepted philosophical view continues to hold that the scope of obligations of justice is defined by membership in a common political community. On this account, people have obligations of justice only to other people with whom they live together under a common constitution, or whom they recognize as belonging to the same nation as themselves." Philosopher David Miller also agrees that obligations only apply to people living together or that are part of the same Nation. What we owe one another in the global context is one of the questions the global justice concept seeks to answer. There are positive and negative duties which may be in conflict with ones moral rules. Cosmopolitans, reportedly including the ancient Greek Diogenes . . . more

https://en.wikipedia.org/wiki/Global_justice