Related Rule
United States of America
Practice Relating to Rule 44. Due Regard for the Natural Environment in Military Operations
Section A. General
The US Naval Handbook (1995) provides: “Methods and means of warfare should be employed with due regard to the protection and preservation of the natural environment.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 8.1.3.
The US Naval Handbook (2007) states:
It is not unlawful to cause collateral damage to the natural environment during an attack upon a legitimate military objective. However, the commander has an affirmative obligation to avoid unnecessary damage to the environment to the extent that it is practicable to do so consistent with mission accomplishment. To that end, and as far as military requirements permit, methods or means of warfare should be employed with due regard to the protection and preservation of the natural environment. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 8.4.
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States refuted the possibility of inferring a principle of “environmental security” from existing international environmental treaties, which would form part of the law of war, being that none of these treaties refers to such a principle, nor was any of them negotiated “with any idea that it [the treaty] was to be applicable in armed conflict”. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, pp. 34–35; see also Written comments on the submissions of other States submitted to the ICJ, Nuclear Weapons (WHO) case, 20 June 1995, pp. 10–19 and Oral pleadings before the ICJ, Nuclear Weapons case, 15 November 1995, Verbatim Record CR 95/34, pp. 64–66.
The United States went on to state: “Even if these treaties were meant to apply in armed conflict … the language of none of them prohibits or limits the actions of States in any manner that would reasonably apply to the use of weapons.” With reference to the 1972 Stockholm Declaration on the Human Environment, the United States maintained that “nothing in the Declaration purports to ban the use of nuclear weapons in armed conflict”. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 39.
Lastly, the United States stated that, although Principles 1, 2 and 25 of the 1992 Rio Declaration had been relied upon to maintain that “the threat or use of nuclear weapons in an armed conflict would constitute a breach of generally accepted principles of international environmental law, … none of these principles addresses armed conflict or the use of nuclear weapons”. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 41.