"New UN legal report addresses the responsibility of states and corporations for environmental damage in conflict", 21 May 2019.

...the International Law Commission’s project to enhance the legal framework protecting the environment in relation to armed conflicts is nearing its end...this summer, seven new draft principles are being reviewed by the Commission...the objective being to adopt a complete set of draft principles together with the accompanying commentaries on first reading during the current session of the ILC...

[Special Rapporteur, Dr Marja Lehto] has proposed draft principle 6 bis on Corporate due diligence, which reads as follows:

States should take necessary legislative and other measures to ensure that corporations registered or with seat or centre of activity in their jurisdiction exercise due diligence and precaution with respect to the protection of human health and the environment when operating in areas of armed conflict or in post-conflict situations. This includes ensuring that natural resources are purchased and obtained in an equitable and environmentally sustainable manner.

Building on the momentum that the “protect, respect and remedy” framework has created, as effectuated in the 2011 UN Guiding Principles on Business and Human Rights, as well as drawing from other non-binding initiatives, such as the 2011 OECD Guidelines for Multinational Enterprises, Dr Lehto has proposed an ambitious draft principle on ensuring the environmentally sound conduct of corporations in relation to armed conflicts. This is particularly focused on natural resources...However, it is likely that this draft principle will be met with scepticism by the international community. Regulating corporate conduct indisputably comprises one of the most heated and controversial issues in the international legal arena...

Dr Lehto has further proposed draft principle 13 quinques addressing Corporate responsibility: 

1. States should take the necessary legislative and other measures to ensure that corporations registered or with seat or centre of activity in their jurisdiction can be held responsible for harm caused to human health and the environment in areas of armed conflict or in post-conflict situations. To this effect, States should provide adequate and effective procedures and remedies, which are also available for the victims of the corporate actions.

2. States should take the necessary legislative and other measures to ensure that, in cases of harm caused to human health and the environment in areas of armed conflict or in post-conflict situations, responsibility can be attributed to the corporate entities with de facto control of the operations. Parent companies are to be held responsible for ascertaining that their subsidiaries exercise due diligence and precaution.

...the second sentence of paragraph 2 might be construed as imposing an international legal obligation on parent companies and, since this understanding is not the mainstream view at the moment, it is quite likely to be met with strong objections...