In January 2026, the OECD released updated Guidelines for Multinational Enterprises on Responsible Business Conduct, introducing new expectations on climate-risk disclosure, human rights impact assessments, and expanded environmental supply-chain due diligence. The 2026 update aligns with science‑based emissions‑reduction pathways, strengthening expectations for responsible conduct in the energy transition. While non-binding, the Guidelines are increasingly referenced by tribunals when assessing whether an investor met baseline due-diligence standards, including under the ‘clean hands’ doctrine. By embedding climate‑risk due diligence into global soft‑law standards, the updated Guidelines effectively integrate corporate responsibility into investment law by the back door, likely shaping how tribunals evaluate investor conduct in disputes involving environmental and social harms.