From its title, one may be tempted to think that this is a text about conventional sources of international law. Chinkin & Alan Boyle rather discuss the parallel; that is, the contemporary methods of making international law (processes, instruments and actors).
States traditionally are the most important actors in international law, other actors are also influential (courts, NGOs, international organizations, individuals and pressure groups), all of which are contributing in the advancement of contemporary international law.
Their various roles are very crucial for contemporary international law making because new global threats and challenges (terrorism, Viruses, climate change, drugs...) also call for new solutions. NATO for instance is aimed at providing a collective umbrella for its members against security threats. The authors concur that for any solution to gain roots, legitimacy will have to be a factor in compliance pull.
The incorporation of natural law theories into international law making (Jus cogens, erga omnes obligations for example) have been useful in uplifting fundamental human values, translated as universal principles.
Law-making, the authors concede must not be the end of the story but rather the beginning, because however sound the law maybe at point in time, there would always be some unforeseeable shortcomings. The collapsing of territorial boundaries with the advent of the internet for example, is one indication why instruments of international law regulations must be strengthened and kept on the alert.