General principles are derived by analogy from rules common to many legal systems. They are not authoritatively codified or set forth comprehensively anywhere
Historically, general principles were included as a source of law in order to prevent a tribunal form avoiding a decision on the grounds that no law was applicable to the case before it and to prevent bias on the part of the judges. Thus, general principles may serve a gap filling purpose. While some argue that general principles must be reflected in treaties or custom, others maintain that they reflect broader general principles of law and international equity. Cohen, Berring and Olson, How to find the Law at p. 486 KF240 .C538 1989
Consistent with the latter view is the idea that general principles are those which are applied universally by state domestic courts (I.e. laches, res judicata, impartiality of judges). Principles that the ICJ has recognized include: freedom of maritime communication, good faith, estoppel, inviobility of the diplomatic agent. Sources of International Law. Martti Koskenniemi (ed.) Aldershot, England ; Burlington, VT : Ashgate/Dartmouth (2000) at page 362. KZ3410 .S67 2000
General principles may be found in the decisions of international tribunals, digests, international law treatises and international law encyclopedias. The best documentation of these principles is found in textbooks, general surveys, or manuals, treatises, classics and encyclopedias. Williams, John W., Research Tips in International Law, 20 Geo. Wash. J. Int’l & Econ. 1, 8 (1986) KZ 3 .W55 1981
Fabián O. Raimondo. General Principles of Law in the Decisions of International Criminal Courts and Tribunals. (Leiden; Boston: M. Nijhoff Pub., 2008) KZ6304 .R35 2008
Cheng, Bin. General Principles of Law,as Applied by International Courts and Tribunals (London, Stevens 1953) KZ3225.C44
Rudiger Wolfrum, General International Law (Principles, Rules, and Standards) in Max Planck Encyclopedia of Public International Law (2010).