Public international law is 'The legal system governing the relationships between countries; more modernly, the law of international relations, embracing not only countries but also such participants as international organizations and individuals (such as those who invoke their human rights or commit war crimes)'.
Thomson Reuters Westlaw, Black's Law Dictionary
'Topics of international law include the law of the sea, the law of treaties, state jurisdiction, international criminal law, human rights, international humanitarian law, and the international law of the environment. Through international law an attempt is made to identify and advance common interests of humanity.'
Lexis Advance Pacific, Encyclopaedic Australian Legal Dictionary
Each jurisdiction's legal system will be structured differently - it is important to understand the source of primary law in a jurisdiction before you start your research.
Provides introductions to the legal systems of many countries. It also provides links to official agencies and (often) English translations of primary documents.
JuriGlobe world legal systems
Provides an overview of legal systems and official languages worldwide and a visual educational tool for comparative and international law. The main areas of focus are: Civil law, Common law, Customary law, Muslim law, and countries with a mixed system.
Provides links to US and international legal information, arranged by subject.
Provides UK and international legal information, arranged by jurisdiction and topic.
Yale country by country guide to legal research
A country-by-country guide on legal research which links to research guides and databases for each country except the United States.
Oxford University Press have created a history of international law, running from 1494 to the present.
This concise timeline maps the broad history of public international law with particular attention paid to the signing of major treaties, the foundation of fundamental institutions, the birth of major figures in international law and milestones in the development of some of the field’s best-known doctrines.