4 Is it law?

The classical objection is Austin's: law is a command backed by a sanction from a sovereign, and international law has neither a legislature nor a police force. The answer is that modern international law has a system of rules about rules — how treaties are made, who may make them, and what happens when they are broken: the equivalent of the secondary rules that make any legal system work. Enforcement is imperfect and uneven, but imperfection is a difference of degree; municipal law enforcement is also imperfect.