What is the law of Buddhism that governs the behavior of the believers?

correct answer is Dharma

Explanation:

Buddhism one of the major world religion

and Buddhism is a faith it was founded by the Buddha (Siddhartha Gautama)

As dharma is the moral order of universe for Hindu

and code of living that fundamental principles of law is religion

5 Precepts are the laws of Buddhism

not killing not stealing not committing sexual misconduct not lying not taking intoxicant

so Buddhism governs the behavior of the believer is Dharma