Final answer:
Customary international law refers to widely accepted practices and behaviors among states. Diplomatic immunity and prohibition against genocide are examples, while regulation of antitrust law and prohibition against price fixing are more specific to national laws.
Step-by-step explanation:
Customary international law refers to the practices and behaviors that have been widely accepted by states as binding and mandatory. It is derived from the consistent and general practice of states over time.
Out of the options given, diplomatic immunity and the prohibition against genocide are examples of customary international law. Diplomatic immunity grants certain privileges and immunities to diplomats to ensure their diplomatic functions are protected, and the prohibition against genocide is a well-established principle that has been codified in international conventions.
On the other hand, the regulation of antitrust law and the prohibition against price fixing are more specific areas of national laws and regulations that may not necessarily fall under customary international law.