The Source of international law is a basic concept in the science of international law. At the same time, it attaches great importance and colorful views in the academic community.

国际法渊源是国际法学的一个基本概念，同时也是一个学界非常重视而又意见纷呈的传统国际法理论问题。

youdao

According to traditional views, the international custom is the source of the international law, while the international practice is not.

传统观点认为，国际习惯是国际法的渊源，国际惯例不是渊源。

youdao

The practice of courts and other law-enforcement agencies is the basic source of private international law in most countries.

法庭的司法实践活动和其他司法机构在大多数国家是国际私法的法源。

youdao

International treaties constitute a major source of international law and are critical to establishing the respective rights and obligations of states in relation to many political, economic, military, environmental and other matters.

BBC: Scotland politics

At least according to a source quoted by National Geographic, namely the International Institute of Space Law, that treaty does indeed apply to private citizens as well as the countries they live in.

FORBES: Sunshine No Longer Free, Says Sun's New Owner