Final answer:
International law is the series of customs and principles that guide relations among nations. Compliance with these norms is largely voluntary and it governs the way states interact with each other.
Step-by-step explanation:
The series of customs and principles that guide relations among nations, wherein compliance with these norms is largely voluntary, is known as international law. International law consists of rules drawn from treaties and customs that govern the way states interact with each other. It provides a starting point for states to weigh possible courses of action and determine how best to respond to any situation.