This thesis offers an interpretation and doctrinal analysis of the undefined, open-textured term “due regard” under the United Nations Convention on the Law of the Sea (LOSC). The focus is on LOSC Articles 87(2), 56(2) and 58(3) under which a state is to have “due regard” to—or, to balance—the rights, duties and freedoms of other states when it exercises its own rights, duties and freedoms. The study proceeds by first considering relevant rules of international treaty interpretation set out in the Vienna Convention on the Law of Treaties, with emphasis on doctrinal debates as to when and how preparatory work (travaux préparatoires, a treaty’s negotiation record, or legislative history) may be used as a treaty interpretive aid. An exhaustive examination of judicial interpretations of the LOSC on this point confirms that recourse to preparatory work is prevalent in the judicial interpretation of open-textured terms under the LOSC. Next, “due regard” is interpreted with reference to the term’s ordinary meaning and context and in light of the LOSC’s object and purpose—and, on the basis that “due regard” is an open-textured, ambiguous or obscure LOSC term, using legislative history to inform and confirm an understanding of its meaning. Finally, balancing methodology in international law and judicial interpretations and applications of “due regard” are examined. The interpretive conclusions are that the duty of “due regard” signifies (a) a relationship based on legal equality, and (b) the shift from traditional laissez-faire freedoms of the seas to a comprehensive, more heavily normative legal order under the LOSC. The practical consequence of the first is that no state enjoys priority in any ocean use conflict beyond the territorial sea simply on the basis of being a coastal or a flag state. The practical consequences of the second are that “due regard” is a more heavily normative and narrower standard than its predecessor “reasonable regard”, and, because it encompasses obligations to the interests of the international community, the specific application of “due regard” must always include ecological considerations, howsoever to be weighted.