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Customary international law is generally binding on all States, but States that have beenpersistent objectors to a customary international law rule during its development are not boundby that rule. 130Assessing whether State practice and opinio juris have resulted in a rule of customaryinternational law may be a difficult inquiry. 1311.8.1 Relationship Between Treaties and Customary International Law. Treatyprovisions may, inter alia: (1) not reflect customary international law; (2) reflect customaryinternational law; or (3) be based on customary law, but not precisely reflect it.In most cases, treaty provisions do not reflect customary international law. For example,AP I’s provisions changing which persons would be entitled to the privileges of combatant statuswere viewed as novel at the time of the adoption of AP I and as not reflecting customaryinternational law. 132In some cases, a treaty provision may reflect customary international law. The rulereflected in the treaty would thus be understood to be binding, even if the treaty provision wasnot applicable, because the rule maintains a separate existence as a customary norm. 133 Forexample, provisions of Hague IV and the Hague IV Regulations have been found to reflectcustomary international law. 134 Law of war treaties have specified that customary law andprinciples continue to apply even if the treaty is not applicable. 135A treaty provision may be based on an underlying principle that is an accepted part ofcustomary law, but the precise language of the treaty provision may not reflect customaryinternational law because there may be considerable disagreement as to the precise statement of130 Refer to § 1.10.1.2 (Legal Force of Customary International Law Among States).131 Michael J. Matheson, Deputy Legal Adviser, Department of State, Remarks on the United States Position on theRelation of Customary International Law to the 1977 Protocols Additional to the 1949 Geneva Conventions at theSixth Annual American Red Cross-Washington College of Law Conference on International Humanitarian Law(Jan. 22, 1987), 2 AMERICAN UNIVERSITY JOURNAL OF INTERNATIONAL LAW AND POLICY 419, 421-22 (1987)(“Having described the reasons why I believe that the topic of this Workshop is important and very relevant todecisions currently being taken with respect to Protocol I in the United States and other governments, it is of coursemuch more difficult to say exactly which of the rules contained in the Protocol currently are in fact a part ofcustomary law. As I am sure you all appreciate quite well, there is no clear line drawn in the dust for all to seebetween those principles that are now customary law and those which have not yet attained the degree of acceptanceand observance that might make them customary law. Instead, there are degrees of acceptance and degrees ofobservance, and the judgment as to what degree of each is sufficient for establishment as customary law isinherently subjective and hard to define precisely.”).132 Refer to, e.g., § 4.6.1.2 (AP I and the GPW 4A(2) Conditions).133 Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. United States), Merits, Judgment,1986 I.C.J. 14, 95 (178) (“[E]ven if two norms belonging to two sources of international law appear identical incontent, and even if the States in question are bound by these rules both on the level of treaty-law and on that ofcustomary international law, these norms retain a separate existence.”).134 Refer to § 19.8.2.1 (Hague IV and Customary International Law).135 Refer to § 19.8.3 (Martens Clause).30