Editorial: To qualify as an effective law, as opposed to merely an impressive declaration, a command must be backed up by an effective enforcement mechanism. That is why societies have police. The power of the police to enforce a society' s laws makes those laws effective. But there is currently no international police force. Hence, what is called "international law" is not effective law. Which one of the following is an assumption required by the editorial's argument? ["The only difference between international law and the law of an individual society is the former's lack of an effective enforcement mechanism.", 'If an international police force were established, then so-called international law would become effective law.', 'Only an international police force could effectively enforce international law.', 'The primary purpose of a police force is to enforce the laws of the society.']